Been doing some research on this and am begining to think, in my case, that it is the hood latch/switch. I had the hood open the day before I started having problems with the alarm not arming. Then a few days later, I had the situation where it armed but the alarm activited about a minute later on its own.

You might want look at your hood/trunk as the source of the problem. Any one out there know how to troubleshoot this problem?