Scanner is connected by network (LAN).(In reply to comment #0)
> Version:           0.2.kde4.2.0-9.5 (using KDE 4.2.0)
> OS:                Linux
> Installed from:    SuSE RPMs
> 
> Brother DCP-560CN scanner, drivers brscan2-0.2.4-0.i386.rpm from
>  http://solutions.brother.com/linux/en_us/
> On KDE 4.1.3 skanlite, kooka and xsane works great.
> On KDE 4.2 skanlite and kooka crashes, xsane interupt without any message. When
> I login in XFCE skanlite, kooka and xsane works fine.
> 
> Program: Skanlite (skanlite), sygnał SIGABRT
> [Current thread is 1 (Thread 0xb5fc8700 (LWP 7130))]
> 
> Thread 1 (Thread 0xb5fc8700 (LWP 7130)):
> [KCrash Handler]
> #6  0xffffe430 in __kernel_vsyscall ()
> #7  0xb6827990 in raise () from /lib/libc.so.6
> #8  0xb68292c8 in abort () from /lib/libc.so.6
> #9  0xb6869683 in ?? () from /lib/libc.so.6
> #10 0xb686aedb in free () from /lib/libc.so.6
> #11 0xb492c91b in close_device_net () from /usr/lib/sane/libsane-brother2.so.1
> #12 0xb492382b in CloseDevice () from /usr/lib/sane/libsane-brother2.so.1
> #13 0xb492f752 in sane_brother2_open () from
> /usr/lib/sane/libsane-brother2.so.1
> #14 0xb64f849d in sane_dll_open () from /usr/lib/libsane.so.1
> #15 0xb64f92c4 in sane_open () from /usr/lib/libsane.so.1
> #16 0xb7db910e in KSaneIface::KSaneWidget::openDevice(QString const&) () from
> /usr/lib/libksane.so.0
> #17 0x0805022d in _start ()
> 
> Kooka:
> 
> (no debugging symbols found)
> (no debugging symbols found)
> [KCrash handler]
> #6  0xffffe430 in __kernel_vsyscall ()
> #7  0xb6992990 in raise () from /lib/libc.so.6
> #8  0xb69942c8 in abort () from /lib/libc.so.6
> #9  0xb69d4683 in ?? () from /lib/libc.so.6
> #10 0xb69d5edb in free () from /lib/libc.so.6
> #11 0xb615991b in close_device_net () from /usr/lib/sane/libsane-brother2.so.1
> #12 0xb615082b in CloseDevice () from /usr/lib/sane/libsane-brother2.so.1
> #13 0xb615c752 in sane_brother2_open ()
>    from /usr/lib/sane/libsane-brother2.so.1
> #14 0xb68a949d in sane_dll_open () from /usr/lib/libsane.so.1
> #15 0xb68aa2c4 in sane_open () from /usr/lib/libsane.so.1
> #16 0xb7d60beb in KScanDevice::openDevice(QCString const&) ()
>    from /opt/kde3/lib/libkscan.so.1
> #17 0x0808847d in ?? ()
> #18 0x08089c1f in ?? ()
> #19 0x08089fd5 in ?? ()
> #20 0x0808a46d in ?? ()
> #21 0xb697e705 in __libc_start_main () from /lib/libc.so.6
> #22 0x080647e1 in ?? ()
> 

Could you try with scanimage?

and also set debug environment variables before starting the application.

$ SANE_DEBUG_DLL=255 skanlite
or
$ SANE_DEBUG_BROTHER=255 skanlite
(this environment variable is a guess it could be SANE_DEBUG_BROTHER2)

But I'm afraid this is probably not a Skanlite bug.

My guess is the brother driver:
> #10 0xb69d5edb in free () from /lib/libc.so.6
> #11 0xb615991b in close_device_net () from /usr/lib/sane/libsane-brother2.so.1


I hope you can file a bug to Brother.

jacek@jpsdesktop:~> SANE_DEBUG_DLL=255 skanlite
[sanei_debug] Setting debug level of dll to 255.
[dll] sane_init: SANE dll backend version 1.0.12 from sane-backends 1.0.19
[dll] sane_init: reading dll.conf
[dll] add_backend: adding backend `brother2'
[dll] sane_get_devices
[dll] load: searching backend `brother2' in `/usr/lib/sane'
[dll] load: trying to load `/usr/lib/sane/libsane-brother2.so.1'
[dll] load: dlopen()ing `/usr/lib/sane/libsane-brother2.so.1'
[dll] init: initializing backend `brother2'
[dll] init: backend `brother2' is version 1.0.1
[dll] sane_get_devices: found 1 devices
[dll] sane_get_devices
[dll] sane_get_devices: found 1 devices
[dll] sane_open: trying to open `brother2:net1;dev0'
KCrash: Application 'skanlite' crashing...
sock_file=/home/jacek/.kde4/socket-jpsdesktop/kdeinit4__0
jacek@jpsdesktop:~>

Program: Skanlite (skanlite), sygnał SIGABRT
[Current thread is 1 (Thread 0xb5f61700 (LWP 5319))]

Thread 1 (Thread 0xb5f61700 (LWP 5319)):
[KCrash Handler]
#6  0xffffe430 in __kernel_vsyscall ()
#7  0xb67c0990 in raise () from /lib/libc.so.6
#8  0xb67c22c8 in abort () from /lib/libc.so.6
#9  0xb6802683 in ?? () from /lib/libc.so.6
#10 0xb6803edb in free () from /lib/libc.so.6
#11 0xb48c591b in close_device_net () from /usr/lib/sane/libsane-brother2.so.1
#12 0xb48bc82b in CloseDevice () from /usr/lib/sane/libsane-brother2.so.1
#13 0xb48c8752 in sane_brother2_open () from /usr/lib/sane/libsane-brother2.so.1
#14 0xb649149d in sane_dll_open (full_name=0x8173be8 "brother2:net1;dev0", meta_handle=0x811b868) at dll.c:1106
#15 0xb64922c4 in sane_open (name=0x8173be8 "brother2:net1;dev0", h=0x811b868) at dll-s.c:21
#16 0xb7d5210e in KSaneIface::KSaneWidget::openDevice(QString const&) () from /usr/lib/libksane.so.0
#17 0x0805022d in _start ()

jacek@jpsdesktop:~> SANE_DEBUG_BROTHER2=255 skanlite
[sanei_debug] Setting debug level of brother2 to 255.
[brother2] brother init
[brother2] brother version: 1000001
[brother2] starting bus scan
[brother2] scanning bus 004
[brother2] found dev 062A/0000
[brother2] found dev 05E3/0604
[brother2] found dev 04CC/1122
[brother2] found dev 0BC7/0006
[brother2] found dev 1D6B/0001
[brother2] scanning bus 003
[brother2] found dev 0A12/0001
[brother2] found dev 041E/4064
[brother2] found dev 1D6B/0001
[brother2] scanning bus 005
[brother2] found dev 1D6B/0001
[brother2] scanning bus 002
[brother2] found dev 1D6B/0001
[brother2] scanning bus 001
[brother2] found dev 1D6B/0002
KCrash: Application 'skanlite' crashing...
sock_file=/home/jacek/.kde4/socket-jpsdesktop/kdeinit4__0
jacek@jpsdesktop:~>

Program: Skanlite (skanlite), sygnał SIGABRT
[Current thread is 1 (Thread 0xb6036700 (LWP 5341))]

Thread 1 (Thread 0xb6036700 (LWP 5341)):
[KCrash Handler]
#6  0xffffe430 in __kernel_vsyscall ()
#7  0xb6895990 in raise () from /lib/libc.so.6
#8  0xb68972c8 in abort () from /lib/libc.so.6
#9  0xb68d7683 in ?? () from /lib/libc.so.6
#10 0xb68d8edb in free () from /lib/libc.so.6
#11 0xb499a91b in close_device_net () from /usr/lib/sane/libsane-brother2.so.1
#12 0xb499182b in CloseDevice () from /usr/lib/sane/libsane-brother2.so.1
#13 0xb499d752 in sane_brother2_open () from /usr/lib/sane/libsane-brother2.so.1
#14 0xb656649d in sane_dll_open (full_name=0x81d4ff0 "brother2:net1;dev0", meta_handle=0x811b868) at dll.c:1106
#15 0xb65672c4 in sane_open (name=0x81d4ff0 "brother2:net1;dev0", h=0x811b868) at dll-s.c:21
#16 0xb7e2710e in KSaneIface::KSaneWidget::openDevice(QString const&) () from /usr/lib/libksane.so.0
#17 0x0805022d in _start ()

Could you do the same with scanimage?

$ SANE_DEBUG_DLL=255 SANE_DEBUG_TEST=255 scanimage

So far it all points to some problem with libsane-brother2.so.1
Could be a compiler version problem: sane, skanlite and libsane_brother2 compiled with different compiler versions.

Unfortunately I do not have SuSE installed nor a Brother scanner.

The next step after this would be to compile libksane...

jacek@jpsdesktop:~> SANE_DEBUG_DLL=255 SANE_DEBUG_TEST=255 scanimage
[sanei_debug] Setting debug level of dll to 255.
[dll] sane_init: SANE dll backend version 1.0.12 from sane-backends 1.0.19
[dll] sane_init: reading dll.conf
[dll] add_backend: adding backend `brother2'
[dll] sane_get_devices
[dll] load: searching backend `brother2' in `/usr/lib/sane'
[dll] load: trying to load `/usr/lib/sane/libsane-brother2.so.1'
[dll] load: dlopen()ing `/usr/lib/sane/libsane-brother2.so.1'
[dll] init: initializing backend `brother2'
[dll] init: backend `brother2' is version 1.0.1
[dll] sane_get_devices: found 1 devices
[dll] sane_open: trying to open `brother2:net1;dev0'
Przerwane
jacek@jpsdesktop:~>

I try downgrade libksane0 from 4.2.0-68.14 to 4.1.3-4.7 and one time skanlite start, but crashed when I try do preview scan. Next time don't start.
I also try same programs (skanlite 0.2.kde4.2.0-9.5, kooka 3.5.10-1.61, xsane 0.996-0.pm.1) run under IceWM and all works. I can place logs. 

> Przerwane

If I googled correctly this indicates some kind off error.
which means that also scanimage crashes :(

This is a really weird bug, but now I'm 99.9% sure that the error is not in Skanlite or libksane.

Since the scanner is "connected by network (LAN)" I wonder if KDE 4.2 somehow interferes with the network...

I'm sorry I can't help :(

I tested (on OpenSuse 11.1 and Fedora 11 Alfa)

kdesu skanlite
kdesu kooka
kdesu xsane

 and scanner works correctly. Probably, there is error in permissions to... (I don't know for that) in KDE 4.2 because before upgrade (kde 4.1.3 on OpenSuse 11.1) all works for "normal" user.