I have a package that does the exact same thing. Here's how it is set up:

1. Package does some import stuff.

2. Execute SQL Task checks table row count:

- Result Set - Single Row

- Source - SELECT COUNT(*) as ProductionCount FROM Table

- Result Set tab

- Result Name - 0

- Variable name - User::ProductionCount

3. Precedence constraint w/ expression checking @User::ProductionCount > 0

Pretty simple in theory, but it seems like I always have to jump through a few hoops to get an Execute SQL task to populate the variable. In this case, I found that I needed to have the COUNT(*) alias match the variable name in SSIS. Wierd, but it works.

Are you using an Execute SQL task to populate your variable?