That's a common problem with the Zen.
Creative was repairing and replacing them under warranty but it was never improved so the problem kept re-occuring
If you can solder and have steady hands, you can fix it once and for all. see below.

A 6 page disassembly guide:
Anatomy of Creative's Zen Micro Audio Player

Also see posts by "algaas" and "duckstardeluxe" in this thread