We did an upgrade from moodle 2.0.3 to 2.1.

When I click on any course inside two specific categories then a blank screen is shown. If debugging mode is enabled there is an error message:
Fatal error: Call to undefined function coding_exception() navigationlib.php on line 1462

The issue MDL-28167 describes a similar problem but in my case only two of 8 categories are affected. Therefore I'm not sure that this issue is related to.