It certainly could be a bug, but unless someone on the dev. team can make it happen, it will be almost impossible to fix.
If you report it as a bug, be sure to include everything you can about your environment (server type, PHP version, MySQL version, etc.).
Have you tried turning off the compress_css and compress_js System Settings, then deleting all the files in the core/cache directory?
Do you have any MODX security ACL entries or Form Customization rules that might apply?
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PLEASE, PLEASE specify the version of MODX you are using.
MODX info for everyone:
http://bobsguides.com/modx.html