Cannot use the FTP upload manager

I'm having a problem with the build in FTP upload manager.
I really like to use this feature instead of a seperate program (like SmartFTP) because I can setup permissions per user. BUT: whatever I try, I cannot get it to work. It keeps coming with the error message: "Unable to connect to the server www.uylenborch.nl"
I'm 100% that the settings are correct (like the FTP hostname and path) because I'm able to FTp with a 3rd party program using the same settings without a problem. What's more: the same PHP Album on a different webhoster does not give any problems when using the build-in upload manager.

So I expect it's something special/tricky with my Webhoster, but I have no clue what and where to look. The web is running on Unix, that's all I know.

Any help from your side would be hihly appriciated. If needed I can email you directly the FTP user account, so you can have a look yourself.

I did a manual install for the PHP Album. But I did that exactly the same on both sites and like I said, one is working and the other not :-(

Sjaak