Version:           0.9.3 (using KDE 3.5.8)
Installed from:    FreeBSD Ports
Compiler:          gcc 4.2.1 
OS:                FreeBSD

I see this with a Canon EOS-350D and a Canon EOS-400D:

Both cameras are correctly auto-detected in PTP-mode.
The images on the camera are correctly displayed in
digikam's preview.
I can retrieve all pictures from those cameras with gphoto2
(command line) without any problems.
Only when I use digikam, the transfer stops randomly
and digikam reports, that there is a communication error.
When this happens I see that there is effectively no
communication as the camera's light does not flash.
I usually can solve this by only mark a single picture,
retrieve this and so on. I tried the other Canon camera
protocol and saw the same problem.
It makes no difference if I manually start digikam or
let it be started through hal.

This is the output of "gphoto2 -v":

gphoto2         2.4.1          cc, popt(m), exif, no cdk, aa, jpeg, readline
libgphoto2      2.4.1          cc, no ltdl, EXIF
libgphoto2_port 0.8.0          cc, no ltdl, USB, serial without locking

These additional ports are installed:
kipi-plugins-0.1.5_1,1 KDE Image Plugin Interface plugins
libkipi-0.1.6       KDE Image Plugin Interface

The funny thing is that I remember not having had problems
with older kde and digikam but cannot reproduce what versions
were ok.
It does not have to do with some settings as I completely
rebuilt kde and digikam when upgrading from FreeBSD 6.3
to FreeBSD 7.0. I also deleted all digikam-related settings.