The value "null" was passed to the "scrapeFil

I keep getting this in the session log.

While I went through the tutorials ok and played with them a bit, whenever I create my own session and scripts I tend to end up with this message in the log and thus no details grabbed.

1. Script - start
2. scrape file - list of links (session var COMPID)
a. For each (after pattern matching) Script - Grab Details
b. Scrape file - details page (using COMPID in the URL)

And that's it.
I know COMPID is being set correctly as it says so in the log.
But when it comes to using it in the second scrape file to get the details, it says "The value "null" was passed to the "scrapeFile" method"

Yeah, I'm a newbie to this so if this is some simpel schoolboy error feel free to point and laugh :)

Any help would be greatly appreciated.
ta