I know you are working on the parser (QP5.dll), so please consider this a “just in case you don’t already know” report.
Try saving the following, erroneous, SQL code into the file “Test.sql”, then open the file into Toad 6.1 Beta:
INSERT INTO Table1 (Column1 FROM BigTable AS bt;
I get a freeze every time and have to kill Toad from the Task Manager.
When I replace QP5.dll in my Toad 6.0 production release with the beta version the same freeze occurs. Restoring the original QP5.dll fixes the problem. Which is a shame because the beta QP5.dll partially addresses some of the issues reported on this thread.