FWIW, I have never managed to flash VANILLA on any of my 3 N900s. Using two different PCs, both 32 bits, running Debian Squeeze, Debian Wheezy, EasyPeasy (basically Ubuntu 10.04) and Windows XP. Flashing COMBINED worked fine in all cases, but VANILLA failed every time. As a conclusion, I do not believe it can be done and treat all reports of people having done it successfully as myths.

Edit rather than reply so I don't bump the thread...

The above was correct as of time of writing. I have since then acquired a new laptop and hey presto, flashing suddenly worked! Weird...