Foren / Cotonti / Support / major php crash???

Hey guys, I have THE weirdest error you'll see in ages!!!!!

Last night, after the restart of my website on Contoti, all was well.
The first sign of trouble, was when ppl tried the minichat: NO refresh, but it redirected to the minichat page after the post...
Then, someone noticed that the forums were... gone...
We have the recent items plugin, and ALL the forumposts are still showing, but when you click on the forum button, the forumsections are empty.
Weird: in the forums configuration in the admin panel, the structure is still there...
Also: When you click on one of the topics on the index in the recent forumposts section, you'll only see the textbox.
When you make a post, nothing happens...
Try to click on the "users" button: empty page, but the users arre there....

I have my test site, so I uploaded the sql file from my live site to that. Same problems, except for the minichat that does work...

Has anyone heard of such an error?
If so, can you please post a solution?
Thing is, Contoti's great, and we do NOT want to start over again...
Thanks in advance, Dave

Added 1 hour 1 minute later:

Okay, small update:

I made a backup of the current sql, just in case.
I dropped all ols sql tables, and installed a fresh one.
Guess what?
EVERYTHING worked...

I have reset it to the "troubled state", because I don't feel like loosing the users, pfs, forums again.
The minichat also works when the sql was restored.
If I have to install a fresh sql:
What boxes should be ticked in sql manager, to save the users?

I prefer the structure to be repaired, installing a new sql goes too far, I really need advise