I'm trying to activate iMessage on my iPad 2 - I keep receiving an error message saying I need to check my connection even though I am already connected through wi-fi and the connection is strong. Please advise.

Possibly there's a firewall in the router. For reasons that I do not understand, that will affect IOS (iPod/iPad) communication but will not affect computers or other devices.

You will need administrative access to the router. If a firewall is present, turn it off and test the iPod again. If it works, turn the firewall back on but weaken it a notch and test the iPod again. Repeat as required.