Error doing git svn rebase

Hello,

I have cloned our subversion repository using git svn clone. Then I have made a few changes
and committed a few times. Now I would like to do git svn rebase before I continue, to be
sure I don't get too much out-of-sync with the subversion repository. However, git-svn fails
like this:

luna:/home/daniel/projects/UMC3D-9.1.git(master)> git svn rebase
First, rewinding head to replay your work on top of it...
Applying: - Doxygen fixes.
Applying: - Code cleanups.
Applying: - Logging fixes.
fatal: Unable to create '/home/daniel/projects/UMC3D-9.1.git/.git/index.lock': File exists.

If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.
rebase refs/remotes/git-svn: command returned error: 1

luna:/home/daniel/projects/UMC3D-9.1.git> git branch
* (no branch)
  master
luna:/home/daniel/projects/UMC3D-9.1.git> git checkout master
error: Entry 'GeoROG/Control/MikrofynAdvancedBladeController.cpp' would be overwritten by merge. Cannot merge.

luna:/home/daniel/projects/UMC3D-9.1.git> dir .git/index.lock
ls: cannot access .git/index.lock: No such file or directory
luna:/home/daniel/projects/UMC3D-9.1.git> git --version
git version 1.6.3.3
luna:/home/daniel/projects/UMC3D-9.1.git> git svn --version
git-svn version 1.6.3.3 (svn 1.6.5)
luna:/home/daniel/projects/UMC3D-9.1.git> 

At this point I am not sure how to best handle this problem. Any help would be much appreciated!

Regards,

Daniel Lidström
Stockholm, Sweden