The C-shell interprets the "command" . as the "current working directory". It tries to execute a current working directory somewhere in the PATH. You can easily verify it using this dummy script:
On my system it results in:
$ chmod 744 test.csh
/usr/bin/.: Permission denied.
The -x option echoes the commands before the execution (first line echoes the dot). As you can see, here the dot (as command) is mapped to /usr/bin/.
hence the permission denied error (since a directory has the executable bit, but you don't have permission to actuall "execute" it).