I recently received the PB that I ordered. Everything is in perfect condition, except two keys, "a" and "i". They make a squeaky sound when pressed and released (more when released). It feels like they are rubbing against something in the keyboard. They function fine, but I'm wondering if anyone has the same problem with their keyboard, and if there is a solution for it. While the keys work, the sounds really get on my nerves (also the vibration I feel as the keys spring back up). Thanks for your help!