Tried searching for this particular issue, or related to the platform, but wasn’t seeing much.
It looks like sometime between 6.0rc14 and 6.0 GA, at least for the mipsbe platform and a number of my RB2011’s, the default-configuration script was wiped. When upgrading from stock 5.x to 6.0, rebooting, then doing a /system reset-configuration (without no-defaults, mind you) is resulting in a nearly inaccessible device. I’ve tested this on a couple RB2011’s (pretty much the only unused boxes I have as they await deployment), and it isn’t limited to a particular box (thinking bad flash/NVRAM or something).
I got in through winbox (MAC address), and sure enough the config was effectively blank. No IP addresses, no firewall rules, zip. So I upload 6.0rc14, downgrade, reboot, and do a /system reset-configuration, and everything reappears.
In 6.0 GA, /system default-configuration print returns an empty script. In 6.0rc14, I see the script.
I see mentions of 6.1 floating around, but they topics include issues that I’m not even getting to yet, so I’m not sure if this has been addressed in some new unreleased version or not. Just wanted to be sure others could confirm, and if the issue has already received attention.