You can fix like this :
The following should be added to all of the forms which POST back to vBulletin or a vBulletin script. This will automatically be filled out with a 40 character hash that is unique to the user.
Code:
<input type="hidden" name="securitytoken" value="$bbuserinfo[securitytoken]" />
I have now disabled it and installed cybchatbox as that is fully working with 3.70 gold