It sounds like you're covering all your bases... not sure what's going on here.
How are you setting your variable value - is it set on creation (in the Variables window on the left) or are you setting it within the flow of your program, such as a ForEach loop or similar?
Check the scope of your variable - is it set at the Package level?
Can you post the exact error message you're receiving?
Tim Mitchell, Microsoft Data Platform MVP
Data Warehouse and ETL Consultant
TimMitchell.net | @Tim_Mitchell | Tyleris.com
ETL Best Practices