Adam/Karen,
I have created an ASP.NET test page/site and e-mailed it to you so that you can recreate this issue: a pasteHTML command executed while using Firefox, for certain settings of editor properties like readonly=true, does not work. The same command executed while using IE to browse this page/site does work as expected.
Thanks for your time in reviewing this issue.
If a resolution is received offline, I will be sure to post it back online here so that others may benefit from it.