Hi folks I have a 2010 mac mini that I changed the Administrator account name, and since then the Yosemite startup progress bar stops at about 25% and lags for a few seconds, then stops at about 50% and lags for a good 10-15 seconds. Before I changed the administrator name the thing was cookin along at blazing speed. It's got a brand new Samsung 850 EVO in it, 8Gb RAM. I fixed permissions, reset pRAM, and eventually I booted the mac up and the system was corrupted and I had to reinstall Yosemite, which automatically updated to 10.10.3. Just updated to 10.10.4, problem has gotten worse. I realize I will probably have to erase the hard drive and start over in order to fix this, wanted to see if someone might have a solution??