Problem uploading documents in shared group directly through filesystem

I have the following problem: I made a private group for me and a friend and we work together on the same document. When I open this document directly from the filesystem integration /home/dion/wuala/direct/.../documents/ I can edit it in OpenOffice (although it's a MS Word document) and save it afterwards. Now, if I have worked for an extended time on this document and made a lot of alterations, and save it afterwards, OpenOffice saves it and I can close the document. However, if I try to open it again from Wuala, I get the message: "File is not uploaded completely, please contact the owner" (which I am myself of course). If I try to re-open it from the filesystem, the file is not recognized by OpenOffice. Somehow the upload to Wuala seems not to work and the file ends up corrupted. The Wuala window does not show anything about 'uploading' the file. So I lost the work done.

This happened two times over the last two days. Making only minor adjustments gives no problems at all so the problem seems related to either the time spent on the document or the amount of alterations made. The second time I made the same big alterations to the file, I also saved the edited file to my own HD and that file is good so I could upload it again from there. But it should upload automatically after the alterations made I would suppose.