[plt-scheme] 299.408 help-desk and old planet libraries

I just downloaded the 299.408 release candidate and notice the following
problem:

Start DrScheme.
Start Help Desk.
Search for anything.

The following happens:

DrScheme Internal Error
exception raised by exception handler: continuation application:
attempted to cross a continuation barrier; original exception raised:
/home/dvanhorn/.plt-scheme/planet/300/cache/schematics/schemeunit.plt/1/1/compiled/info.zo:
read (compiled): code compiled for version 299.106, not 299.408

Removing the 300 directory in planet and restarting DrScheme fixes the
problem.  (Surely having old planet libraries shouldn't crash the Help
Desk, right?)

David