vBulletin 4.x Problems after upgrade - "Invalid Forum specified"

[webgroup]

Hello, after upgrading to 3.6.0, sometimes when I click on a forum it says:

"Invalid Forum specified. If you followed a valid link, please notify the administrator"

If you refresh the page or try again it works.
It happens all the time, sporadically on any forum.
This is really hurting my site.

Please help.

Thanks.

[webgroup]

*Also when this happens the URL shows like this:
http://www.mywebsite.com/forums/a/

it replaces the name of the forum with an "a".

[Mert Gökçeimam]

Hello George ,

Do you have any cache option enabled on vBSEO Cp ? If yes can you please try disabling it to see if the error will be present or not

[webgroup]

It appears the problem is solved after disabling and enabling the apc cache. Also I was not aware that I needed a different prefix for the cache if I am running more than one instance of vbseo in a server. So I set it up with a different one.
I'll let you know if the problem comes back.

Thanks Mert!

[Mert Gökçeimam]

Great to hear