You can upgrade ImageMagick manually. Its not tough enough. You will need to login to server as a root user using SSH and you can upgrade ImageMagick as:
cd /usr/local/src
wget ftp://ftp.imagemagick.org/pub/ImageMagick/ImageMagick-6.5.1-0.tar.bz2
tar xjf ImageMagick-6.5.1-0.tar.bz2; cd ImageMagick-*
./configure --prefix=/usr
make; make install
cd PerlMagick/ ; perl Makefile.PL ; make ; make install
cd ../../; rm -rf ImageMagick-*