I have tried to import blender files to Unity. I have put them to my projects Assets folder. Then I can find them under Projects. However, I cant put them to the scene. It says Blender could not convert it to an FBX file. I am using 2.54.
I have done most of my models in 2.54, so is there any way make it work with Unity? I dont want to do all the work again in 2.49.
Yes, although, instead of importing automatically, you have to manually export from blender to your project's assets folder. Select the objects you want to export, then click File->Export->Autodesk FBX. From there, just navigate to your Unity project's asset folder. (Change the export options in the left panel.)
IF you have no animation you need to import from blender 2.5x, get the stable blender 2.49b release and import your file there and export as .fbx !
Else you can search at http://www.graphicall.org/builds/ for a custom build with a working .fbx exporter (dont know if one exist), for the future I recommend to use the 2.49b version.