I used it with my 3g set without any issues
Did you use the toolkit to install a custom recovery on your 3G set? I think the problem comes when installing a custom 3G rom. If you're using a grouper (n7 wifi) custom recovery to install a tilapia (n7 3g) rom, there will be errors such as "status 7". Not sure if the toolkits have updated their custom recoveries to the appropriate ones. Which toolkit did you use Btw?