I have 2 routers here in my house, both using WPA2 Personal.
With the older one (Linksys WRT54G with DD-WRT custom firmware) I have no problem, everything works fine.
But with the newer one (Linksys WRT-160N) sometimes my phone asks me the password (even with the password previously saved on the phone) and says it's wrong after I type it. All I need to do is unplug the router from the power outlet for a few seconds and then turn it on again. But I had this problem with my old iPod touch too, so I think this router just sux...