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...
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[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]?
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Pedro Lopes
contacto: jazz@radiozero.pt
website: http://web.ist.utl.pt/Pedro.Lopes