"Update unsuccessful" on all apps running on SD card
How many internal space do you have (check on Settings &gt; SD card &amp; phone storage settings &gt; Internal phone storage &gt; Available Space)? Make sure to leave at least 15-20 MB of internal space (probably larger if you have a large number of large apps) so you can safely update apps. If you have little internal memory left, then updates will fail and "Update All" will fail en masse. The solution is to update the apps one by one, or to clear up some space in the internal memory.

I never had problems with updating apps installed in SD card except when my phone's internal memory reaches about 5-10 MB.