Version 0018 of the Arduino software.
Windows 7 Home Premium
Every time I verify or upload a sketch I get this message "Couldn't determine program size: null". Other than that everything works fine. Not a major problem, but I imagine sometime in the future if I attempt to write a too large of a program I won't really know.
I'm not certain if the problem was fixed in 0018 but in previous versions there are problems if the Arduino software is installed in a path that includes spaces.