check out failed

cvs server: warning: cannot open /home/cvsroot/CVSROOT/val-tags read/write: Permission denied
cvs [server aborted]: cannot read /home/cvsroot/CVSROOT/val-tags: Permission denied
*** Checkout Failed:

But using tortoiseCVS, I can do this successfully.
What can I do ?

This appears to be strictly an issue with file/directory permissions on the server. Since jCVS does nothing more than log-in using the information you provide, I would first ask if there is any difference between the logins? If not, then the other other possible difference is that jCVS is performing an operation (such as watches) that tortoise is not performing. In either case, this is definitely a server issue and one of permissions. I would look at the CVS server file in question.