With Gimp for raster graphics and Inkcape for vector drawings, Linux is a graphics platform whose speed, stability and functionality and last but not least lack of clutter will suprise even jaded Photoshop and Illustrator users. However, there were until recently a few quirks in the data exchange between the two applications. Inkscape can export to the Gimp default file format XCF since version 0.44, but the saved files could throw the
GIMP XCF image plug-In could not open image
error upon opening the saved file in Gimp, which may be preceded by errors such as
*** (inkscape:13460): WARNING : Format autodetect failed. The file is being opened as SVG. (…)
when saving with Inkscape.
The cause of this error is discussed here
with the solution and patch here:
So you should update to the latest version of Inkscape, currently 0.46.