What's wrong with my HRM watch? Going crazy on me

I have a Polar 150 model.

I noticed last week there appeared to be some condensation inside the watch. I don't wear the watch to swim nor in the rain.
At the end of a run last week, I hit the button to retrieve my workout info and the display just freaked out on me. Started scrolling through all the different screens and I even heard a little bit of "static" as if it was short-circuiting.
I opened it up to check the battery, put it back in and it seemed to be working fine.
I go to run yesterday, put it on my wrist and it starts freaking on me again.
I tried it today. Was working fine - then about 2 1/2 minutes into it, it starts to freak out again, including that static noise. I just took it apart - and it's running fine.

Any thoughts? I wish it was just the battery going, but I'm guessing it's not.

Edited by runnerx 2009-07-01 12:06 PM