I hate it when this happens.
I've got a ClickOnce application that I've created for a top secret project I'm working on for MS (via 3 Leaf, of course). Only I built it on v2.0.50215.44 of the Framework, and deployed it on a server, loaded with one of the SQL Server 2005 CTP versions. I sent it on to QA, and ClickOnce just won't work - it can't seem to push the files down as needed. Sure enough: the QA server was built with a SQL Server 2005 CTP, but with v2.0.7something.
So my first thought is to ask Google - to see if anyone has blogged about versioning issues with ClickOnce. Only, ClickOnce is ALL about versioning (i.e. people grab an executable from a server, which opens up a secure/sandboxed .NET app pool and runs locally - and the executable can be configured to check for versioning updates on the server - all so that versioning isn't an issue with your applications (pretty cool eh)).
In other words, searching for information about the version of the Framework that ClickOnce is running from is pointless - just about every thing out there about ClickOnce will be about versioning, and the Framework. Google returns so much info, and there's really no way to fine-tune the query... It's that place where Google breaks down. (I mean what do you type: "Framework version clickonce" etc.)
*sigh* Guess I'll just go recompile my app in a higher version of the framework, and see if that will then work on the QA .7something builds...