Arduino support for CEDET is really new, as in I posted the first stable CEDET release with it included yesterday, so I'll guess I'm one of a very few people using it at the moment.
I have the Arduino 1.0 package installed for ubuntu, and had work a few shenannagans to make it happen. My version is 1:1.0+dfsg-6.
The basic doc for the arduino support is here:http://www.randomsample.de/cedetdocs/common/cedet/Arduino-Features.html
The error you see is from loading a version number from this file:
and it is expecting something like "1.0", which is needed so it can create the right kind of Makefile.
I suppose a simple solution would be to edit version.txt to "fix" the version.txt file. Personally, it would be helpful to me if you could join the CEDET mailing list and work through how to get a reliable version number with me there so we can fix this for everyone.