Ok, Ok, Ok, I already know, I am using beta…
But anyhow, is there a fix that I am not aware of to make Unity work with Blender 2.56a beta? Right now I am working around by manually exporting as a FBX, and it works great. But… If there is some simple fix to just work with the dot blend files with this version of Blender, I am all ears.
Latest download of Unity, Blender 2.56a beta, Windows 7 64bit
/nitpick
I actually faced a similar issue earlier today, I have not tried this yet but here is my plan: install two copies of Blender, and make Blender 2.49 the default application to open .blender files. That may allow you to work manually with Blender 2.56a, while Unity uses Blender 2.49 for it’s import.
A side issue may be, though, that integrated editing (opening .blender files from the project) should end up opening with 2.49, a side work for that side effect would be to keep the Assets directory open in explorer so you can open the files with the Open With option.
I have not tried it yet is because I faced the issue in a mac, and as far as I know, there is no way to make any application the ruler of a file format there.
I have in the past tested working with both versions (in a Mac) and it seemed the file format remained exactly the same, so I was able to jump back and forth between versions to use features I liked more in 2.5.