LIST command goes idle for 30 seconds

Hi,

Please help me with this weird problem:

I use a Win XP computer to connect by ftp to an Apache webhoster server. I use a flat rate ISP. I get connected to the server by ftp and I can upload and move through the folders but every time the command implies a LIST, it takes 30 seconds of no activity and then the LIST is executed.

For example:

chdir
.... ok, well executed
LIST
Connecting data socket... (this missage appears immediately)

[ At this point it remains 30 seconds freezed]

... executes list command
... ok message


The strange issue is that with the same computer and ISP, I can get connected to another webhoster I have, a Win IIS server in this case, and the LIST command is executed fast and easy.

I have tried it removing all firewalls, antiviruses, etc. and using CuteFTP, WSFTP and even ftp> prompt at DOS and the same bad result.

By the contrary, I tried to connect by ftp to the Apache server with anyother computer, again with Win XP but a ADSL ISP in this case, and the problem does not happen.

I even asked the Apache webhosters to reinstall my account but no good result again.

Any idea on why this happens? Is it because of the ISP?

TIA