Maybe you're missing this with the download from extras-devel:

Enable the extras-devel repository http://wiki.maemo.org/Extras-devel
as root:
apt-get install libblas3gf liblapack3gf pymaemo-optify python-numpy

Are blas and lapack fixed in extras-devel?
(Fix broken blas and lapack for python-numpy:
as root:
cd /usr/lib/
ln -s libblas.so.3gf libblas.so
ln -s liblapack.so.3gf.0 liblapack.so

It's instructoins from anders_gud from the first post on how to install 0.7.1.
Just a thourght on what could be wrong. It sounds alot like the problem i first had when i installed Mypaint 0.7.1 and re-did the steps above and then it worked

Or you could start it up from xterm maybe that would give you a clue?

e: Asked qole about the touchscreen pressure sensitivity and this is his answer
I have yet to figure out how to get pressure sensitivity to work inside Gimp on any of the Maemo devices. Unless someone gives me some hints, I don't know what to try next.

And it is even less likely that it will work in LXDE, since it is running in a lightweight nested X server that probably doesn't transmit the pressure values. But I could be wrong...

Sorry...