Well, first we need to know where it locked up (some strange file maybe?)
So, does the lock up depends on the setting of quick, standard or thorough test? Does it locks up if archives scanning is turned off?
If you go to the Settings and select the "Report file" page, you can turn on creating the report file. If you check "OK files" to be included in the report as well, all the scanned files will be included in the report file. So, when it locks up, the "bad" file should be at the end of the report file (or the file at the end of the report file should be "close" to the bad one, if it's not there itself).
If you find the approximate location, you can try to scan ony the file/folder to check/find the "bad" file...