Hamster acting crazy - death immenent?

Question
So my wife used to have a dwarf hamster that was pretty mild mannered and fun, but then one day it just started going nuts!  It wouldn't stop running around in the cage, running in the wheel, trying to climb the water bottle and everything.  Then the next day he was dead.

Now the problem is that we have a black bear hamster and he's starting to exhibit the same symptoms: trying to climb out of the cage, running crazy in the wheel, etc.  She even bit my wife like the last hamster did.  We're afraid that this one is going to die too.  What would cause something like this?  Thanks for any help.

Answer
Well how old was the dwarf hamster?? Dwarf hamsters only live about a year and it may have had a heart attack. In reality i've seen a lot of hamsters play on the wheel constantly and then the next minute they are dead. I call it sudden death syndrome. I believe that it's something internally wrong with them like a heart problem and you don't know about it. It can't be passed from one hamster to another. How long have you had this hamster that you currently have now? I know for a while when you first get a hamster they tend to stay on the wheel all day long and night. My hamster stayed on the wheel for two weeks straight and never got off. I was amazed he didn't die of a heart attack. Now he sleeps all day.