Website suddenly stopped working

I'm using Fashion for a website and it all worked perfectly fine uptil now, but now I suddenly get this message on every page at the frontend:

Oops, you've encountered an error 1064
It appears the page you were looking for doesn't exist. Sorry about that.

What can be the problem?

Hi,
1) Have you installed extra plugins or modules ?
2) Try to change template to default - and check.
3) Change "Error Reporting" to FULL - on Global Configuration and Debug System [On]
4) Search Engine Friendly URLs [Off] and check

Hi, I'm also using the Fashion template (QUICKSTART), which worked fine until I messed with the home page (see below). I'm now also getting this same error "Oops ... 1064". I had made a second Home page menu item (Single Article) with the alias "Home-2" to test and made it the Featured Page, deselecting the original Home page. After the test, I switched them back and even deleted the test and got the 1064 message. I've tried to clear the cache, but still get the error page. I switched the default template to beez_20 and am able to see the home page. Switching it back to Fashion, still get the error page.

Any further thoughts on a solution?

Thanks,
Railer

UPDATE: I read in another post from teitbite that this error can be caused by an article or K2 item that doesn't exist but is being called to display by a module. In my case, there were several NSP GK4 modules trying to display apparently non-existent K2 items which were causing the problem. To solve it, I unpublished each module and reloaded the page, going through each module until I found the culprit.

Hope this helps.

Railer