I'm with @M'vy - Don't use the VPN. For that matter, don't connect to the compromised network at all by any means. Contact the appropriate help desk, network administrator, and/or incident response team and advise them of the situation. Don't plug into the network or connect via VPN until they've neutralized the threat to the best of their abilities, and given the "all clear".
If, for whatever crazy reason, you absolutely must connect to the compromised network, do so from a system booted to non-writable LiveCD. Additionally, make sure all non-disposable, writable media (including internal HDDs) have been physically disconnected from your system. Last, make sure you do not transfer any sensitive information across the compromised network unless absolutely necessary.