Outlook 2007 Error formextension.dll

Hi,

When we open outlook on one of our machines running XP Pro/Outlook 2007 we get and error report with the mod-name formextension.dll in the error signiture and outlook atempts to restart unless you untick dont restart. This carries on in an ongoing circle so we cant run outlook.Have searched and not seem to have found the answer. Any help aprieciated….