Subscript out of range

I have an asp page which connects to a SQL database, and requires login. If I attempt to the load the page in IE, I get absolutely nothing (just a blank white page with no error messages at all). If I attempt to load it in Firefox or Opera, I get the following error message:

Microsoft VBScript runtime error '800a0009'
Subscript out of range: '[number: 0]'
/KnowledgeBase/sos-kb.inc.asp, line 82

And here are the lines of code in question:

Line 80 Dim CurrentDomain, AuthInfo
Line 81 AuthInfo = Split(Request.ServerVariables("LOGON_USER"), "\", -1, 1)
Line 82 CurrentDomain = AuthInfo(0)

The site was working absolutely fine and for some reason, one day, it just stopped loading.

Any help would be appreciated.Uhm... when you load it in IE, view source. Do you see anything?

What have you recently changed?