Known issue : New version of Companion is on the way
We contacted IBM about this and they replied with the following:
Thank you for your report.
This a known problem with Companion 2.0.5 when using a server set up for session-based authentication. We have submitted a fix to the App Store, however it may take up to two weeks for a new version to appear there. In the meantime, you can work around the problem by temporarily disabling session authentication on the server, or creating an Internet site document with an Override Session Authentication rule in place for "/servlet/traveler*", both of which will allow Companion to work using basic authentication.
We apologize for the inconvenience and hope to have a new version of the app available shortly.
IBM Lotus Notes Traveler Team
Feedback response number WEBB8SDBNA created by Simon J Laird on 03/14/2012