Satoshi client does not update when run through a VPN

[picobit]

When running the Satoshi client (Bitcoin-Qt) while I have VPN enabled (Mullvad), the client often does not get new blocks.  It quickly gets eight connections to the network, but apparently none of them hand out any blocks.  I have heard that there are many "leaching" servers by now, perhaps if I get one of them it refers me to its peers, and behind a VPN no-one else can find my client.

Is there anything I can do to avoid this?

[Eternity]

Check your firewall something might have blocked the connection after that

[Moebius327]

Try to forward Port 8333 in the VPN settings?

[picobit]

Try to forward Port 8333 in the VPN settings?

Thanks Moebius and Eternity for your suggestions!  I will try that.  Sometimes it works through the VPN, sometimes it doesn't.