all filters are lost when file is saved as .png or when opened with other tool

Binary package hint: inkscape

Saving as.svg works but when viewed withe a image viewer the picture looks nothing like it looks when opened withe inkscape.
When saved as .png filters are ignored and the image looks like the original without any filters.
when i use a filter and try to save it as .xcf it displays the following:

Traceback (most recent call last):
  File "/usr/share/inkscape/extensions/gimp_xcf.py", line 173, in <module>
    e.affect()
  File "/usr/share/inkscape/extensions/inkex.py", line 207, in affect
    self.effect()
  File "/usr/share/inkscape/extensions/gimp_xcf.py", line 38, in effect
    pageHeight = int(self.xpathSingle('/svg:svg/@height').split('.')[0])
ValueError: invalid literal for int() with base 10: '340pt'

It saves the file but gimp is not able to open it.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: inkscape 0.47.0-2ubuntu2
ProcVersionSignature: Ubuntu 2.6.32-22.36-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-22-generic i686
NonfreeKernelModules: fglrx
Architecture: i386
Date: Wed Jun 16 19:04:30 2010
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100427.1)
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: inkscape