FYI- Here's 3 methods to patch the Master Key vulnerabilities on a Gingerbread D2. Not all will work for everybody, but at least one should work for most. Also, there's currently 3 known Master Key related vulnerabilities. The 1st patch method only covers 2 vulnerabilities, the 2nd may cover 2 or 3 depending on your luck, the 3rd method covers all 3 but is least applicable to a wide audience.
"Master Key" vulnerability fix - Droid 2 / R2D2 / Milestone 2 / Droid 2 Global - RootzWiki