I tried this on the current version of QGIS 2.10.1-Pisa (OSGeo4W install) under Windows 7 Pro. It worked fine. It gave me these results:

print lat, lng
7.97335663032 54.2128392776

Then I tried it on Ubuntu 15.04 with QGIS 2.10.1-Pisa. QGIS crashed. I even tried this:

try:
   lat, lng = transform(in_projection, out_projection, 887590, 7210569)
except:
   print "Unexpected error:", sys.exc_info()[0]
   raise

and that didn't help. The resulting error message when running QGIS from the prompt:

Segmentation fault (core dumped)

I also tried import pyproj; pyproj.test(), under QGIS shell. It worked fine on Windows and Seg-faulted on Ubuntu.

I think this is an issue with the QGIS software, not with pyproj.

Feel free to reopen. Closing due to inactivity & likely unrelated to pyproj.