Error : Length cannot be less than zero. Parameter name: length

System.ArgumentOutOfRangeException: Length cannot be less than zero.
Parameter name: length
   at System.String.InternalSubStringWithChecks(Int32 startIndex, Int32 length, Boolean fAlwaysCopy)
   at System.String.Substring(Int32 startIndex, Int32 length)
   at Http.ParsePairs(String s, Char sep, NameValueCollection C) in c:\Documents and Settings\All Users\Documents\Qaaz2\Source\Http.cs:line 113
   at ApplicationBase.Init() in c:\Documents and Settings\All Users\Documents\Qaaz2\Source\ApplicationBase.cs:line 14
   at Application.ProcessRequest(Http h) in c:\Documents and Settings\All Users\Documents\Qaaz2\Source\Application.cs:line 1218