Over on the Baen Bar, someone complained that he had bought an e-book from Barnes & Noble to read on eReader on his Palm, only to discover B&N had changed the format and was now selling in eReader-encrypted ePub that his Palm couldn't read.
Curious, I went to the B&N website and investigated, and wrote my findings up for TeleRead
It's all very confusing. Their site gives no hint that they have changed formats to an incompatible version apart from only listing four compatible platforms. They continue to use the name "eReader", but don't make clear even in their FAQ that they are now format-incompatible with Fictionwise eReader.
(This is also mentioned in this E-Book Devices thread on Mobileread