If you create a debugging log that includes this error, we can look into why it's happening.
If you're using the GUI client, select Help->Capture Debugging Log, then go to the main screen and reproduce the error adding a shelveset, then return to the debugging dialog and save and email the log file to firstname.lastname@example.org.
If you're using the command line client, rerun the ccollab command and include the --debug option as the first argument, e.g.:
ccollab --debug addchangelist new myshelveset
This will create a ccollab.log file in the current directory - email it to email@example.com.