dude i have the same thing going on here.... so tired of this. I even bought an AVR ISP mkII to change the bootloader , changed the Atmega 8U2
nothing with both environments 0.22 and 1.0 the same.
I run XPsp3 and have perfectly working atmel mcu on the board. I can't believe that i bought one more after this (an arduino Ethernet) and it turned out that the firmware was incompatible to FTDI usb2serial adapter - needed a firmware change.
The reseller from robotev.com (yes it is a genuine arduino) didn't offer me a replacement or fix.
Guys i bought it so to concentrate on application not the HW. I design hardware all day and this thing ruined at least 5 Saturdays of mine and like 45+35+50 Euro
I really liked your stuff before i bought it.