404 errors after install of 3.8.3

[محروم.كوم]

Hi folks - Just updated to 3.8.3 last week, then suddenly about 3 days ago I am no longer able to login as my admin account nor any other user. I'm getting a "page not found" or 404 error.


What's odd is that content spammers are somehow still creating new accounts and posting spam as recent as a few minutes ago, however I can not create new accounts. RSS Feeds are still being posted fine, it seems that I have just lost control of vBulletin.

I have been trying to contact the ISP that installed the upgrade (and uninstalled vBSEO at the same time as it was conflicting with vBadvanced) and I have been unable to get any response from the ISP either, which is extremely strange as thier support has been 100% top notch until the last week (yes I have paid my hosting fees - LOL!)

Any ideas appreciated.
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