Ok I've tested this on my test site with only VBulletin version 4.0.5 (older version than production sites in case the production versions are the fault)
I have VBGallery version 3.00 installed and no plugins.
I have the exact same problem when receiving emails whilst in the gallery. The url is duplicated.
To replicate this you must have notify pm's via pop up enabled for the user and then click ok
when the popup tells you that you have a new private message. Now you will be presented the the open message in a new window box... click OK
to that as well.
Now you will be looking at an error 404 page. Take a look at the url and you will see that the domain url is incorrect.
It should read
But instead reads:
I can now replicate this on three websites.
I've checked and double checked the urls for compliance with VBulletin and VBgallery and they are correctly set up.