Issue opened here: http://code.google.com/p/arduino/issues/detail?id=958

What board are you using?  The Arduino Mega 2560 does have an on-board USB-to-serial convertor.  (Or did yours die somehow?) 

You might try changing the stk500v2 protocol to "wiring" in the boards.txt file (in hardware/arduino in the Arduino software directory).

The arguments to Mouse.move() are relative (i.e. changes to the current mouse cursor position).  Can you post the full code for the keyboard programs you're having trouble with?

Weird.  Which board are you using?  I don't think there's anything different in this between 1.0 and 1.0.1; are you sure it doesn't work the same in both? 

I think this is a problem with the Polish translation.  It included a translation of an internal string (used as a Date format); the translation makes the string invalid and there's an exception on startup.  You could try putting your computer into a language other than Polish or editing the editor.languages.current preference in your preferences.txt file (e.g. setting it to "en").

See: http://code.google.com/p/arduino/issues/detail?id=942

The problem seems to be that the computer isn't seeing the Arduino board at all.

Maybe try a different USB cable?  Or if you've been going through a USB hub, trying plugging the board directly to the computer.

Unfortunately, it's not really possible for us to support boards from other manufacturers, since we don't really know how they work.  I'd recommend asking the maker of your board for help. 

Do you have the same problem with Arduino 1.0?  Testing it would help isolate the changes that caused this problem to occur.

For example, in Arduino 1.0.1, we added the "--relax" flag to the linker options, which helps with large programs (http://code.google.com/p/arduino/issues/detail?id=729).  It's possible that the issue you're seeing is a side effect of that change, for example.

What board are you using?  The new Arduino boards (like the Uno) don't use the FTDI chip or drivers.  When browsing for the driver file, select the main "drivers" folder (not the "FTDI Drivers" sub-folder). 

We have a list of distributors here: http://arduino.cc/en/Main/Buy

For example, Adafruit in the US: http://www.adafruit.com/products/849

Or the Arduino store here: http://store.arduino.cc/ww/index.php?main_page=product_info&cPath=11_12&products_id=225
http://store.arduino.cc/ww/index.php?main_page=product_info&cPath=11_12&products_id=226

Bemused, if you're using an Olimex board, you should ask them for help.  Unfortunately, we can't support other people's products (because we don't know how they work, etc). 

Does it appear in unknown devices?  Can you then update the driver?  See: http://arduino.cc/en/Guide/Windows and

The PDF should be the same as the Eagle files.  The two ATmel chips are different footprints for the same chip, so either can be used depending on availability. 

Weird.  Did you already have those files in your /Library/Java/Extensions folder?  What if you delete them?  (The Arduino software should come with its own copy of those files.)

I'd suggest asking DFRobot for support.  It's hard for us to provide advice on other people's boards.