It's a bug of the current IDE and it affects every OS (@eried: it's not related to Linux :P)
It's related to the localization. If you select the english language the bug won't appear anymore. It only happens when you select a different language. The bug has been already fixed and next IDE 1.0.2 won't be affected. At the moment you can download the development version of the Arduino IDE or select the english language.
Here my previous thread:
http://arduino.cc/forum/index.php/topic,111450.0.html
Here the ticket:
http://code.google.com/p/arduino/issues/detail?id=964&can=6&sort=-id