This is a known issue with HTC since the GB update, f you do a search you''ll see there are alot having the same issue.
The only fix is a factory reset but the problem will come back, I myself have had to reset 3 times already and I've given up and installed a different alarm app from the market.
HTC has commented that a fix will be in the works, but will not say as to when it will be pushed out. I went to a VZW store and they had no clue as to what is going on
I'm having the same problem with the alarms. Did a couple of factory resets, tried adding an HTC clock widget to one of my homescreens(couldn't even select the clock after adding the widget). I had to buy a third-party alarm app--Alarm Clock Extreme--to get my alarms to work. Is there any way to downgrade to Froyo?
I downloaded Alarm clock plus as well, but from what I have read, it is not worth doing a hard reset to your INC 2 just yet. The reset will cure the problem temporarily, but any changes may make the widget appear lost to the operating system. HTC is aware of the issue and working on it. Here's a link to the lates page as of 9/30/2011. http://community.htc.com/na/htc-forums/f/124/t/12556.aspx?PageIndex=7