Is there a Calling Rule limit?

I am running a Asterisk 1.4 with the GUI installed. Using the Calling Rules setup I have created Dialplan #'s 1-7, no problem. When I create Dialplan #8 it deletes Dialplan #1 on the GUI but not in the extensions.conf (context = [custom-numberplan-1]) file. However Dialplan #1 will not work, unless I delete Dialplan #8. Is there a limit to the number of Dialplans I can create?
Thanks in advance for any help.