I've been working on getting a custom board using an ATMega328P-PU chip set-up on my Windows 7 PC. It initially appeared under my Device Manager as Atmega16U DFU, so I downloaded FLIP and flashed the Uno R3 firmware into it. The board then shows up as Arduino UNO R3 in my Device Manager. I open up the IDE, select the appropriate COM port, verify and upload. When I try to upload I get a "avrdude.exe: stk500_getsync(): not in sync: resp=0x00" error. I've tried unplugging/resetting the board and reflashing the hex file. I can upload my program to a default Arduino Uno, and the device manager shows no differences.
The only difference I can see between the two is one has a 1311, and the other has a 1440 on it, which I assume are date codes. Any advice?