Quartus 12.1 crashing alot

12.1 and 12.1 SP1 are barely usable for me (web edition in Win7 64) just for routine builds. I get internal errors during fitting that kill the process and dump out a stack trace. I have to cross my fingers with each build, because it's only around a 50% success rate. The errors are repeatable, but they come and go inexplicably with minor changes to code or timing constraints. Last time I filed a service request regarding a Quartus error Altera told me to buy the full version, so I assume there isn't anything I can do in 12.x without shelling out money. Removing db directories between builds doesn't make a difference. Archiving and extracting a "fresh" version of a project doesn't help, either.