XP-Dev.com

Hi, there.
Is there any problem in accessing with Tortoise from behind a proxy or firewall?
I talked with the network administrator and he said there is no restriction about the XP-Dev domain.
Tortoise keeps retrieving this message:
"Server sent unexpected return value (400 Bad Request) in response to OPTIONS
request for '<http://svn.xp-dev.com/svn/my-project-name/trunk'
The operation failed."

At home I’ve accessed OK.

Thanks in advance.