Created attachment 69494 [details]
New crash information added by DrKonqi

kontact (4.8.0) on KDE Platform 4.8.1 (4.8.1) using Qt 4.8.0

- What I was doing when the application crashed:

Default message format is plain text.

1) Create a new email message.
2) Switch the format of newly created message from plain text to html.
3) Try to type something in the message text field.

Kmail/Kontact crashes.

-- Backtrace (Reduced):
#6  0x00007f5d5cb3c5e3 in eventFilter (e=0x7fffc4645f20, o=0x11f32b0, this=0x3187100) at ../../kdeui/sonnet/highlighter.cpp:355
#7  Sonnet::Highlighter::eventFilter (this=0x3187100, o=0x11f32b0, e=0x7fffc4645f20) at ../../kdeui/sonnet/highlighter.cpp:337
#8  0x00007f5d5b3bb788 in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=<optimized out>, receiver=0x11f32b0, event=0x7fffc4645f20) at kernel/qcoreapplication.cpp:986
#9  0x00007f5d5bdaf0cf in notify_helper (e=0x7fffc4645f20, receiver=0x11f32b0, this=0x7b52c0) at kernel/qapplication.cpp:4551
#10 QApplicationPrivate::notify_helper (this=0x7b52c0, receiver=0x11f32b0, e=0x7fffc4645f20) at kernel/qapplication.cpp:4527

Bug resolved but if someone could have an explanation :
I see that i have two dictionnaries for my language in identities setup (my language is french and i have "Français" & "Français/France") 
"Français/France" was selected, and crash happens, when i selected other option : "Français", no more crash when writing!

I can confirm that the dictionary change solved the problem for me as well (openSUSE 12.1, KDE 4.8.1 from openSUSE's KDE Release 4.8 repositories).
I had the two dictionaries "Norsk (bokmål)" and "Norsk (bokmål) (Norge)", and selecting "Norsk (bokmål)" solved the problem.

Looking the the System Settings, I see that for the default spell check it is "Norsk (bokmål)" which is selected, but "Norsk (bokmål) (Norge)" is available - as well as "Engelsk (USA)" which seems impossible to get rid off even if I install proper English (i.e. the British English).

Could the error be caused by a migration which forgot to update KMail's identity settings?

I think it would be an improvement if we could select "System default" as language in KMail's identities settings. That way, if my preferred language became available after installation I could switch the language in the system settings and KMail would be using the new dictionary as well.

*** Bug 295636 has been marked as a duplicate of this bug. ***

Created attachment 69601 [details]
New crash information added by DrKonqi

kontact (4.8.0) on KDE Platform 4.8.1 (4.8.1) using Qt 4.8.0

- What I was doing when the application crashed:

I was trying to type reply to an email. This happens every time and makes Kmail unusable.

-- Backtrace (Reduced):
#6  0x00007f27996fc383 in eventFilter (e=0x7fff19542970, o=0xd915340, this=0xead2560) at ../../kdeui/sonnet/highlighter.cpp:355
#7  Sonnet::Highlighter::eventFilter (this=0xead2560, o=0xd915340, e=0x7fff19542970) at ../../kdeui/sonnet/highlighter.cpp:337
#8  0x00007f2797f74678 in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=<optimized out>, receiver=0xd915340, event=0x7fff19542970) at kernel/qcoreapplication.cpp:986
#9  0x00007f279896967f in notify_helper (e=0x7fff19542970, receiver=0xd915340, this=0x1bf2e00) at kernel/qapplication.cpp:4551
#10 QApplicationPrivate::notify_helper (this=0x1bf2e00, receiver=0xd915340, e=0x7fff19542970) at kernel/qapplication.cpp:4527

Try to set and save your spellcheck/dictionary settings. It solved this issue for me.

(In reply to comment #3)
> Could the error be caused by a migration which forgot to update KMail's
> identity settings?

no, the error is caused by bad programming practices

you can work around the bug by setting "Norsk (bokmål)" instead of "Norsk (bokmål) (Norge)" - but if you manually switch back to "Norsk (bokmål) (Norge)" you'll see the bug again ... you can hardly accuse the migration process in this case if you just select something within the configuration dialogue

btw, this is duplicate of bug #295615

Created attachment 69942 [details]
New crash information added by DrKonqi

kontact (4.8.0) on KDE Platform 4.8.1 (4.8.1) "release 483" using Qt 4.8.0

1. Got an e-mail
2. Pressed reply
3. Wrote a line of text
4. Hit Enter to begin a new line

Then application crashed.

-- Backtrace (Reduced):
#6  0x00007f5ec11d5553 in eventFilter (e=0x7fffb7e61bc0, o=0xc081e0, this=0x14a4750) at /usr/src/debug/kdelibs-4.8.1/kdeui/sonnet/highlighter.cpp:355
#7  Sonnet::Highlighter::eventFilter (this=0x14a4750, o=0xc081e0, e=0x7fffb7e61bc0) at /usr/src/debug/kdelibs-4.8.1/kdeui/sonnet/highlighter.cpp:337
#8  0x00007f5ebfa23a28 in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=<optimized out>, receiver=0xc081e0, event=0x7fffb7e61bc0) at kernel/qcoreapplication.cpp:986
#9  0x00007f5ec0436e4f in notify_helper (e=0x7fffb7e61bc0, receiver=0xc081e0, this=0x6422f0) at kernel/qapplication.cpp:4546
#10 QApplicationPrivate::notify_helper (this=0x6422f0, receiver=0xc081e0, e=0x7fffb7e61bc0) at kernel/qapplication.cpp:4522

Set and save spellcheck/dictionary settings solved this issue for me too!

Fixed in kdelibs 4.8.2 (will be released next week)

*** This bug has been marked as a duplicate of bug 297062 ***