Im having a similar problem in my netbook, I have pd-extended installed from a deb package and if I try:
pedro@bird-nb:~$ sudo apt-get install --no-install-recommends puredata
I get him trying to remove pd-extended...
[sudo] password for pedro: Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: libflite1 libftgl2 libgraphicsmagick1-dev libmp3lame0 tcllib libgraphics-magick-perl tcl8.5 libgraphicsmagick++3 libgraphicsmagick++1-dev tk8.5 libquicktime1 libimlib2 freeglut3 libmpeg3-1 libfaad0 Use 'apt-get autoremove' to remove them. The following packages will be REMOVED: pd-extended The following NEW packages will be installed: puredata 0 upgraded, 1 newly installed, 1 to remove and 0 not upgraded. Need to get 0B/1,584kB of archives. After this operation, 4,366kB of additional disk space will be used. Do you want to continue [Y/n]?