I have just had the UI lock up and had to be closed, in the windows non-responsive pop-up, see images.
I have tried to upload the documentation files relating to this to the ftp location as 7zip file, DavidRavastUIcrash.7z but keeps failing error 550, but I’m not sure if that is just the read permission issue (not allowed), but it seems to be something else as on dial-up a 750KB file would take longer to upload. So I don’t know if it got there or not.
Did that happen only once? On the second picture it seems that the Avast version is 5.0.374, not 5.0.377, but maybe it’s just a typo. I hope you’ll get an answer to your the problem ASAP. 
It happened only once.
I don’t know where it gets its data from as I only used an early beta for a short time and used drive image to restore my last backup image, so there would be no trace of that earlier build.
My install was using the Cnet download for 5.0.377, so it looks like the file properties for the avastUI.exe file haven’t been updated to reflect the 5.0.377 version, see image. Or nothing in the UI file changed from 374 to 377, having checked there are a lot of files marked 5.0.374, you could check your file properties.
My problem is not knowing if the ftp worked and they got the 7zip file.
David
The only version of 5 that I have ever installed is the one installed yesterday, which says it is version 5.0.377, however AshQuick.exe, Ashupd.exe, AvastUI.exe, Sched.exe and VisthAux.exe are all still stamped 5.0.344.
Well, I asked that question during the Beta testing here:
http://forum.avast.com/index.php?topic=53487.msg453626#msg453626
Vlk’s reply appeared to suggest that in a Release build the
numbers would be synched. Doesn’t seem to have happened.