Flash uploader depending on server side settings?

Ok, I’ve got quite a strange problem for you, regarding the flash uploader (oh no, not again!) in WordPress. Here’s the deal:

I got to accounts with my webhost (surftown), both with the exact same settings, Linux server.

On both accounts I have several domains.

On my first account, where I host three WordPress installations, the flash uploader works as intended. I can even choose to change it to the browser uploader within the media popup-window.

On my second account, where I have two WordPress installations and none of them show the flash uploader when uploading media. I tried reinstalling wordpress, emptying the cache on my computer, tried the function on several other machines, different browsers etc, but nothing works. WordPress doesn’t even let me select between the flashuploader and the regular browser uploader.

This is becoming extremely annoying since I have to upload images one by one, just like in the not-so-good old days.

I’ve contacted the webhost and they’re looking into it but couldn’t find any solution so I thought that maybe someone here have been through the same issues. Do we need to change something in our server side configuration?

Cheers!