This is a not so uncommon error:
But when I switched to I got a bit confused:

Seriously w t f happened here? Has my RAID controller gone berserk on the poor file?

A couple of weeks ago I saw something similary happend on a production server (VPS).
Suddenly one of my static HTML-files contained fragments of code from something completely different.
As far as I can tell, these errors seems to originate from a broken file system.
Perhaps one should take stuff like this as a sign that it might be wise to start replacing the disks in the raid array.

A couple of month ago all sites died on one of my old servers (a Windows 2003 based Virtuozzo VPS).
I wrote a line about it in one of my previous posts, at least one static HTML-file contained fragments of code from something completely different.

One of the first observation I did on the server was that every site had their own strange error even though almost everyone was running the same version of Umbraco.
As an example, one site did not start at all while another could start but would end up crashing after a couple of hours and bringing down the whole server again. (Not just the application pool.)

I quickly migrated all critical sites from the server leaving just one behind. Today I decided to fix the one that was left behind and also try and determine what was wrong with the server. After a bit of digging I managed to find one useful error message.

Exception Details: System.IO.IOException: The file or directory is corrupted and unreadable.
And my good friend google told me that this might just be an issue with the ASP.NET file cache. I quickly located the cache in :
 C:\WINDOWS\Microsoft.NET\Framework64\v2.0.50727\Temporary ASP.NET Files\root

Deleted all folders in it...
..and IT WORKED!

So note to self, next time IIS/ASP.NET starts behaving strange, try cleaning up the temp files first.