Hey Stimpanzee,
Were you noticing that the RAM was filling up before the freezing occurred?
If your memory gets out of control again, let it grow as high as you feel comfortable with. Then bring up the console with ~ and enter memreport -full. Rename the extentions on the .memreport file to .txt in the [ProjectName]/saved/Profiling/MemReports and then attach it here.
-.
PS - Could you send your dxdiag for good measure?