Care to explain that one?

Am I correct in assuming that you know how to flash the N900 and you know that this is done by the boot loader (NOLO), which runs, like, when you turn on the N900?

I cannot possibly imagine what relation this may have with PC Suite mode. This is something that you select (PC Suite or Mass Storage) when you connect via USB with the Maemo desktop up & running, which will never be the case when you flash.

And remember:
1. forget about cold flashing,
2. re-download and re-double-check that you have the latest images of both fiasco and vanilla.

There are reports that downgrading the firmware may lead to a non-functioning GSM firmware.

And please, post the exact output of your flashing session. I want to see when you see anything about PC Suite mode.