You may have a defective bluetooth card, but it would be best if you had some other device to test it with. It might be that your mouse is bad, or even that the batteries are getting low. If this is an Apple magic mouse, take it in to an AASP or Apple store. There was a bad batch of two of the early BT keyboards and magic mice, and so there's a specific diagnostic program for testing those. Reasonably sure Apple doesn't consider that a customer facing program, so you'd have to take it somewhere to be run, and then they'll just tell you whether or not it passed. Your system should still be under warranty, so if the device is found to be bad, it should be taken care of under that warranty.
And when your laptop goes into sleep mode, all wireless connections, including bluetooth, are disconnected. It would be normal for it to take a few seconds to reestablish communications.
MacBook Pro 17 purchased 12/28/10
My Bluetooth Mouse quits working every couple of days. It only occurs when I wake it up but not every time. Sometimes if I reload Safari it works - sometimes not.
Going to Mouse Preferences shows it trying to connect.
Green light on bottom of Mouse blinks.
Reboot cures it.