Media upload hangs – the process hangs forever!

I am experiencing a weird problem .. Sometimes when uploading images to my blog, I get a HTTP error. Trying again usually works (the same picture!) but the major problem here is that the async-upload.php script never ends.

I have checked my Apache status and have several of these in the “W” state, which basically means they never end, as I’ve been told.

Doesn’t matter what max_execution_time I have set for php scripts..

How do I stop/reset them? Do I have to restart the whole VPS? And how do I troubleshoot the problem if it only happens sometimes?

It happens with clean installs as well, so no plugin problem. I have checked similar problems in the forums, but haven’t found one that hangs only sometimes..

Thanks for any suggestions