I got the crash-on-Fictionwise-or-eReader-logon behavior, too.
This was the response from Fictionwise:
Version 2.0 of the eReader reading application for the iPhone and iPod touch was recently released. The new version has already been downloaded thousands of times and is working successfully for our users. However, a small percentage of our users are having problems when logging into their eReader.com or Fictionwise.com bookshelf from the application. This issue can be solved by removing the eReader application and re-downloading it from the App Store.
To delete eReader:
1. Press and hold the eReader icon on the iPhone or iPod touch screen until the icons begin to shake
2. Touch the "X" in the upper left hand corner of the eReader application
3. Press the device's [ ] button to stop the rest of the icons from shaking
After eReader is removed, re-download it from the iTunes App store.
Please check the web page below for updates concerning this issue.
We apologize for the issue and we appreciate your patience.
eReader.com Support Team
Bummer. Looks like I'll have to make a list of all the books I've synced in the past (from eReader *and* Fictionwise *and* my own collection), their bookmarks and the like, before trying the "fix."