3.0 Moved From Win2000 To Win2003 (convert Problem)

I got a new server with Windows 2003 on. I moved a site that works fine from a Windows 2000 server. On many pages i get a convertion like this:

|Microsoft VBScript runtime error '800a000d'
|Type mismatch
|
|/test/test.asp, line 3
|

This is the code that i run to get the error:

|<%
| a = 1
| if a = 1 then response.write("a = 1")
|%>
|

It does work if i add "if cint(a) = 1 then...." but is it a way to make IIS6/ASP don't check the code so critical?