In our company we have a BES sollution for our Blackberries.
The users are setup to have access to our internal network resources.

However one Blackberry, a Torch 9800, can't access the internal network.
We have wiped the device already, recreated the user account on the BES but the user still has no access.

All other have no problem.

Moved to the appropriate section.

Do you have any other devices with OS 6? Are they working? The browser works a bit differently on OS 6 than it has in the past, so you may want to review the following RIM knowledge articles to determine whether you need to make some adjustments in your environment:

KB23699-Simplified browser selection in BlackBerry 6

h ttp://docs.blackberry.com/en/admin/deliverables/18232/BlackBerry_Browser-Technical_Note--1231352-0804050608-001-5.0.2-US.pdf