Firefox Default program settings being wrecked by installer

[Shark007]

your registry post has some interesting entries.
some of the terminolgy does belong to my software but I have no idea how it is getting into the Firefox HKLM key.

my software doesnt write these values to HKEY_LOCAL_MACHINE - it writes to HKEY_CLASSES_ROOT
So, somehow, Firefox is re-directing/re-interpretting my intension and using it for itself. very stange indeed.

Do you disable UAC?