n93 problem!

i installed a theme the other day it and it worked fine, then i took out the
memory card(using the remmove option) it of course dissapeared as it was on
the card, it then wouldnt show anything on the screen when it was restarted,
when it finally did, all the contents of the card were missing(still visible
on the pc) anyway the card now works again but when i go to install the
themes it installs it, then right at the end it comes up with "unable to
install". i tried both to phone and card but still nothing, would a reset do
the trick(dont know the code!) or would that lose the snake and other games
along with everything else
thanks
PJ