I've had the same crashing / freezing / not responding since the beginning of my upgrade to Webuilder 2010 (currently 10.2.0.121). Problem has occurred on 3 different Win XP computers.
Scenario:
Working on file with 1000 or more lines of PHP code.
Inserting and editing a new line prior to ending the line with a semicolon. It only happens when the line of code is incomplete with no ; terminating the line.
Webuilder freezes (eternal hour glass). Trying to click anything on Webuilder window results in "(Not Responding)" appearing in the title bar. In a test, I waited 24 hours, and Webuilder still was not responding.
Solution is a Windows Task Manager "end task". All work is lost.
It only seems to happen if it's been 30 minutes or more since the last save of the file - lol. (this is probably just my bad luck, and not a cause).
Below is a screenshot of the crash tonight. The red arrow shows where I was last typing (note, no semicolon termination on this new line I was inserting)...

I am hoping someone else had the same problem, or can duplicate this so Karlis will be willing to fix the bug.
Cheers,
-Gary.