Sounds like there may be some debris in the fill valve (ballcock). Can you describe what it looks like and maybe I can help.

My thought is, you might be able to 1. Turn off the Angle Stop. 2. Remove the top of the ballcock. 3. While holding your hand over the top of the ballcock, open the angle stop a little bit to flush any debris through the stop, supply line, and ballcock. 4. Carefully re secure the top of the ballcock and give it a shot. [:I]
Possibly some additional help here:
http://www.cyberssite.com/plumbing.h...t%20Problem s