Hi dahomme,
This is a common problem encountered by many (myself included).
Its is caused by an incompatibility of Flash with several browsers and its caused by at any time when too many players are on.
You have probably noticed this same problem on sites like Youtube, especially when you have more than one tab open.
So this is a Flash problem and unfortunately we can't do anything about it! :(
I'm getting problems with Previewing Sounds. Using Firefox 3 and have also tried with IE Tab.
The first few previews work fine but then further previews load but don't play. Even dragging the scrub bar won't force any sound to play.
In IE Tab after a while I get and error dialogue
"Internet Explorer can't download. Unspecified Error" although the sound does also play.
Using XP latest service packs/updates all installed.
Any ideas?