Digital Workshop

Hi - been developing a piece of software for 5 years now, but have encountered a problem today. Added some new pages to program - run fine in testing and on XP desktops, but in Windows 7, on every laptop we've tried, the software seems to crash; always at one of the same 2 or 3 points on the new screens.

Will be trying to identify whats causing this tomorrow, in order to fix it - just wondering if anyone could give me some suggestions of the most likely culprits, to give me the best possible chance of solving it. We sell this software worldwide, so the solution can't be to simply upgrade some firmware or drivers on laptops - it has to be a universal fix. Anyone got any ideas of what might be causing this? We dont have any video files in program.