Thanks I'll keep an eye out for that.

I might be really off here, I have no idea about tcl/tk, but could this have something to do with the connection being closed while there's still some pending activity, like the message send still running? Because if I leave enough time after sending a message then this does not occur, only if I send a message then sign out a couple of seconds later.

I was able to reproduce it on first try.
Login -> Send a message -> Sign out -> Crash

Unhandled exception at 0x0045e2a6 in wish.exe: 0xC0000005: Access violation reading location 0x6d6f6397.

>   tk85.dll!0045e2a6()    
    tk85.dll!0042bc8d()    
    tcl85.dll!1006c565()    
    tcl85.dll!1006c748()    
    tcl85.dll!100407f8()    
    tcl85.dll!1000c8f0()    
    tcl85.dll!1000d31e()    
    tcl85.dll!1000cdbb()    
    tcl85.dll!10060598()    
    tk85.dll!00471c33()    
    tcl85.dll!1004e7dd()    
    tcl85.dll!1008b43a()    
    tcl85.dll!1000a8f9()    
    wish.exe!00401062()

I send a message (ie. a goodbye) then sign out. -> wish.exe crash.
A sign-in, sign-out afterwards does not reproduce the issue. I didn't close the conversation window before signing out, and it has been open for some time. It's happened 2 times so far.
Can anyone reproduce this? I'll try testing it some more tomorrow if not.