Best error message ever.
Got this on a web site - WTF - what device?
Card reader, CD drive ... not on a web site, mate!
Turns out this is during a create on a user or a group in AD where the name is greater than the allowed field length.
So for Create User - the SAMAccountName can't be greater than 20 characters,
There's probably a similar restriction for group since I got the same error.
Good interview question :-)