Can you use a tool to watch what's happening? A debugger, protocol analyzer or trace listener for example.

Take a break; Look at a painting.

Don't trust a bug report until you've seen the problem with your own eyes.

Just because other people think it's a bug doesn't mean it's really a bug.

Put the problem aside and work on something else.

Go outside and get some fresh air.

Work from home for a day.

Post the problem on a forum or news group.

Switch off your monitor and sit at your desk quietly for a while.

Before software can be reusable it first has to be usable.

When did it last work? what has changed?

Backtrack.