hmm never had one of my repaints crash FS before :P firstly, try agin to see if it was a fluke! if it still crashes.. make sure all the files you've edited are saved in the right format, ie 32Bit or DXT3 ONLY 8) use imagetool, or dxtbmp
Get dxtbmp here:
http://www.mnwright.btinternet.co.uk/"Graphics tools" on menu, then CFS/FS graphics programs, then DXTbmp (ignore that is says CFS2/2000, it works up to cfs3 and FS2k4)