I just bought a 05 Trailboss and it was running great with no problems yesterday. I turned it off and tried to turn it back on and it won't start.  It will pull start and run fine, but not w/the key.  I'm hearing a clicking sound by the battery.  Battery is good, area w/clicking sound is good.  Don't know what else to check, please help!  

Is the battery charged up ? If so the starter may be bad, possibly the solenoid. The sprag gear on the starter can be replaced if that is locke dup  

try running a wire to the starters' positive post directly from the battery. see if the starter is locking up.
if it is the starter you'd be alot better off buying an aftermarket starter than buying oem.  and it will be alot cheaper to buy aftermarket as well.

the problem is that the design of the engine allows water to get into the side cover and wet both the stator and the starter.
this usually causes the stator and the starter to go out prematurely.
which polaris will not pay to replace under warranty.

....and yes the oem parts are super expensive to replace....

go aftermarket