Same deal for me. Cliq on T-Mobile, was set to to auto for which data network to use. Was working as of late last night because I had new email when I woke up, but as of about 7 AM PDT nothing was working (RSS, internet, email). Switched it to 2G and that works fine.
When I switch it back to 3G (or auto) it "thinks" it's working because it shows data activity (up and down arrows next to the 3G icon) and of course it doesn't auto switch to 2G. Pretty irritating.
I'm going to go check out the T-MO Cliq forums, I suspect there'll be more complaints over there, maybe a rep will respond.