Cant launch Parallels after upgrade to snow leopard

Hi

I have been running parallels 5 on Mac 10.5.8 for some time, just upgraded to snow leopard, and now when I try to launch I get the following error message :

Unable to connect to Parallels Service.
Make sure that the prl_disp_service process is active and it is not blocked by Firewall. If the problem persists, contact the Parallels support team for assistance.


And parallels wont launch

what should I do to fix this please ?

Is this best done by a complete reinstall ?