It's been awhile since I've used a lookup transform, but is sounds like you need to have the data types match on the join columns. So either have them both be numeric or string. I'd lean toward putting a CONVERT() in the query in the Lookup to convert that value to string to match the incoming data.
Jack Corbett
Consultant - Straight Path Solutions
Check out these links on how to get faster and more accurate answers:
Forum Etiquette: How to post data/code on a forum to get the best help
Need an Answer? Actually, No ... You Need a Question