I just upgraded to the 4-20 release of WinAVR and AVRStudio 4.11, got my makefile fixed up, found some changes in the libraries I had to accommodate (including an error in the eeprom.h library that claims a whole bunch of AVR's are no longer supported because their EEPROM control registers moved, which is nonsense, as the references are symbolic) and got everything compiled.
I then created a new project based on the .elf/dwarf file and got the following error message from AVRStudio:
"Coordinator and error occurred while reading the object file. The file may be of wrong type or corrupted, or the object file reader is not up to date.
Error loading object file main.elf"
I suppose I've done something wrong, but of course I don't know what. I've set the makefile for dwarf-2 format and get compiler/linker output that is about what I'd expect.