Yehuda,
When you say EVM6678 you mean the one with or without the XDS560v2 Mezzanine card? In other words, is your board the L or LE version (check here)?
The error message indicates CCS can't recognize the emulator attached to your system. Does the "Test Connection" button runs without problems? Also, did you follow the installation instructions to properly create the udev rules necessary to initialize the device drivers? For details, please check the Linux Host support page.
Older releases of CCS had an issue with the Mezzanine cards (nowadays they are all fixed). However, check this thread which contains useful information that will help you identify the presence and correct initialization of device drivers.
I tested the board without the Mezzanine card in my Linux installation of CCSv5.4 and it worked fine - although I am running Ubuntu 10.04 64-bits. I will have my other board with the Mezzanine on Monday and could give it a spin then.
Regards,
Rafael