I finally managed to import all models to JME, however one last problem remains.
In three of the models the animations appear distorted in JME, although they look fine in Blender.
I tried changing the swap axis to -xzy in the Export menu (this had fixed the problem in the other models), however in these ones the distortion remains.
If anyone has any time to spare, here are the models:
http://dl.dropbox.com/u/69517768/Models.zip
The version of Blender I’m using is 2.62.
Thanks a lot for your time.