variables

I am having a problem with losing a variables value. What I am doing is taking the value from a database, 'customer_id', and putting it into a hidden form value called 'customer'. When I hit submit on the form it sends me to a page where it does several queries to several databases and pulls information all based on the value $customer. I have the individual queries in include files. It does the first 2 queries fine,but when it gets to the third, the value of $customer seems to be gone, so I get no result for the rest of the query's. I looked in my scripts but can't figure out any reason it would lose this value. Any ideas? Thanks, Scott Kalbach