I'm no expert on the matter, I just got it set up with hissin's help.
I would check the connection from the viper box, or whichever your running now, to that purple switch. Did you solder it on or just use a butt(s/p?)connector?
testing all the connctions with a basic 12v test light would be a good idea. Test the purple/yellow wire to make sure it's the right one, test the viper/alarm output to see if it's giving you a 12V pulse, and check at some point on the purple/yellow wire if you're getting a pulse when you activate the alarm module
... that's all I can think of checking right now.
hmm, you might want to make sure your ground and power wires are connected to your module correctly. an incorrect ground or a power cable connected to an accessory and not a constant 12V source could cause wierd things to happen.
where is all your wiring tapped into? a picture would help