There is also possibility that some other program conflicts with SAI.
Maybe antivirus software. Or vice versa - there is virus on your computer, that conflicts with SAI
I've heard about similar problems 2 or 3 times, but for me SAI works everywhere (I tested it on WinXP without service pack, WinXP SP2, WinXP SP3, Vista, Win7 RC, Win7, windows on real computer and windows inside virtual machine. it even works in Linux with wine).