Error message - Unable to save recording The Audio disk may be full

         I'm using Cakewalk Pro Audio 9 on Windows XP with all the updates/patches available. I'll do some recordings using 13 tracks at once and have no problems and then out of nowhere it will stop during a recording and give the message " Unable to save recording The Audio disk may be full". After that it keeps on happening even after closing Cakewalk and restarting it. My PC has an Athlon 64X2 Dual core running at 3.11 GHz with 4 Gig of Ram (using 3.5 due to 32 bit limitations) and a 500 Gig hard drive. Does anyone have an answer for me or something I can try to resolve this issue. Also I have turned off everything that runs in the background (msconfig) and even tried changing the virtual memory from system controlled to 100 Gig to see if that made any difference, but it didn't.