WPA/WPA2 with my Nexus 7
I've read about that phenomenon of some Androids having trouble in mixed WPA/WPA2 mode a couple of times now. As you described, people solved it by using either WPA or WPA2 (or even WEP).

So WPA2 only you tried (but got trouble with your Mac). Any chances to pin it to only WPA? WEP would be a last-ressort, as it offers only marginal protection.

Remark: Not sure about your settings for this, but in some cases people had SSID broadcast turned off on the router; turning it on again (i.e. broadcasting the SSID) solved the issue for some of them.