Invalid procedure call or argument: 'Mid'

Just, all of a sudden got the following error message in several asp pages at once:

Microsoft VBScript runtime error '800a0005'
Invalid procedure call or argument: 'Mid'


It seemed that from one moment to the other, IIS did not understand the straightforward VBSCRIPT function Mid anymore. Googled around a little bit, and found lots of others also had this problem. Not only with Mid, but also other statements like Left and Instr. The point is, between a working state of all my pages and this error message, I've only been doing some database updates, and no changes to asp files whatsoever.

It could only mean I had something else going that Mid being an unknown function. At the end it turned out there was a problem in one of the database fields Mid was referring to: a field supposed to show a link to some document contained the document link without the extension .htm added. Now this Mid was starting it's work. However, inside the Mid there's something like Instr(dbfield, ".htm") searching for ... of course an htm not being there.

Other than complaining about this, or some other error the only thing the engine could come up with was this invalid procedure call... at least, I'm happy not to be the only one around with this problem