I personally wouldn't buy a product, regardless of who made it, that said it found problems on my PC and offered to fix it only if I bought said product especially when my PC was running fine.
I would ignore it. I have noticed a few postings this week about Zone Alarm firewall and there does seem to be some "problems" with the latest update. To be honest I'm considering switching to another free firewall like comodo and ditching ZA, at the moment I've stopped it updating itself till I make my mind up.
If there are problems with it its a damn shame as I've been using it for years and been very happy.