I am running Yaf Dev 538 @ Ubuntu Karmic 64bit (eMirage compilation). When i am trying to save render from GUI a message "Render couldn't be saved" appears above the rendering progress bar. Doesn't affect Win platform. Enabling autosave creates a file in the same directory (so I guess that rights to write in the dir are assigned properely for blender-bin, but maybe there is something with the Qt part - I am using QT4 ver 4.5.3really4.5.2-0ubuntu1). Sending rendering result to blender does the job partialy, but I need two versions (with and without alpha) and saving only from blender would force me to render everything twice!

Edit:

I have found a way round. Close the GUI, click "Close Without Saving" than "Result to Blender". Now you haeve image YafRender viewable in UV/Image Viewer. Now in scene panel in "Format" tab (the place where the rendering resolution is set) you can see 3 buttons. BW, RGB, RGBA. When RGB chosen, we will get the sky color, when RGBA whe have premultiplied alpha in background. You can also set the default output format here. In the end you just need to save the image from UV/Image viewer. I always thought that color space buttons doesn't work with images, just with Blender Internal Renderer (alpha premultiplyfication for textures are independent from those switches, set in the texture panel). Well, thats all, but I would like to outline that this is only a workaround and the problem is still unresolved. GUI saving doesn't work.