Altona,
I fixed the updater by doing the following:
1)Run the updater
2)after it crashes, go to wherever you installed planeshift.
3)look for an updater.zip, it should be dated whenever you ran the updater.
4)unzip updater.zip into the planeshift directory, it should ask you if you want to overwrite the existing file, say yes.
5)run the updater again if all went well, it will update properly, and not crahs

Hope it helps,
-Andy