I get the occasional lockup as well but not after a fresh start. Usually, if ive been rendering all night and next day pause the program to do something; when it comes time to start it again it appears to render at 10% usage thereafter or lockup. Only way ive found around it was to save after the evening, then restart bryce from stratch when its time to continue the picture. Given im playing with the diamond tutorial in a 1600x1200 pic it appears to want a few days to render at a quality of 'super' with maximum ray depth 30 and tir of 28. Take into account the raw file is 94 megs and uses 240megs total in win2k. It does seem though if i leave bryce 5 running not doing anything for a day or 2 just playing around, the whole system gets laggy. Ive never seen this before in win2k but it happens all the time in 98 or me.