script works fine alone, but not when included - what could be the cause?

[xwishmasterx]

I have created a script (single file) that works fine when testing it alone, but when included it doesn't and rest of page is blank.

 

What could cause this? Is this because of some "mismatch" between the queries, variables used on the included file and the existing file?

[teddyb]

Would be helpfull if you could post the scripts