Bearing in mind I've only owned a P. irminia for about 3 days, I haven't seen this particular behavior, there are some general tips I can offer.
First of all, P. irminia is an arboreal tarantula. What you have looks to me like more of a terrestrial setup (and it doesn't *look* humid, although looks can be deceiving). She needs height, stuff to climb on. Check out RobC's P. irminia care sheet for info on housing: http://www.arachnophiles.com/Psalmopoeus-Sp-.php (Note: care sheets can be useful sometimes, but it's not gospel!)
Given that, it could be showing signs of stress due to not having a more vertical setup. Mine (3") is in a 5 gallon long turned on its side, with about 5" of substrate (and a cork tube, which it has decided is less interesting than the silk plant). She's made a tube near-ish the bottom of the plant and stays at the entrance.
Second, the tarantula WILL NOT STARVE. It's going to take a lot more than 2 weeks without food to starve it. Try months. Probably many months. If you're not comfortable giving it food, then don't.
Hope this helps!
---------- Post added 02-12-2012 at 02:18 AM ----------
For what it's worth, tarantulas in the wild will close themselves off if they don't have enough humidity. It lets them retain the humidity that is there. And, of course, premolt is a possibility, but I think the enclosure is more likely the issue.
Search the boards for pictures of P. irminia enclosures (or avic enclosures - same idea - or really, any arboreal enclosure.) to get some ideas.