as this is clearly an internal error, the first thing to do is to upgrade your HFSQL server if it's not at the last version, as any new version of HFSQL can manage older programs.
If HFSQL is at the LAST available version and you STILL have the problem, then the next thing to do is to contact pcsoft, as, once again, this is clearly an internal error...
But... if you had the problem last week, and reindexing fixed it, and you have the problem again, I have to ask:
Did you do a checkdisk?
Did you think about changing WHERE your DBs are stored on the disk?
Did you think about replacing the disk?
because in my experience, problems solved by reindexing and coming back later are a sign of the hard drive dying on me.