CLIP Locked up now not recognized by computer

I plugged my Sansa Clip up to my iMAC tonight to charge (first time on this machine).  Once it was done, I removed it but forgot to unmount it and in doing so it locked up.  I performed the soft reset by holding the power button up for 15+ seconds and it successfully shut down.  But it would not reboot when I turned it back on and now neither windows or mac recognizes the unit.  

Any ideas on how to resolve or does it need to be tossed? 

I tried the soft reset as well as turning on the unit and holding the center button down while connecting to the iMAC again…and nothing.  Tried it three different times and held the center button for over a minute and nothing happened.

Any way to force a hard reset?

Thanks

Tim 

That was the difference…I did not have the switch in the down position when I connected.  I put it down, held the center button, and whalla!  Thanks for the assistance!