I've noticed that too (that the par2 tab stops responding from time to time) and have pulled my hair out for ages trying to figure it out, but haven't ever been able to tie it to corrupt par2 files. Now it makes sense.
RDL, if this you are going to be able to fix this, could you please also add the feature to save the par2 tab status/info whenever the queue is autosaved too? If the program crashes, then all of the par2 info is lost since the last time the program was started, which is a pain if kept running for a week or more...
The REAL Joe