Hi, try Force Quitting the Finder if possible. Maybe have Activity Monitor open next time to help Force Quit things that aren't responding. If not you'll have to power down the Mac.
We might find some clues as to the problem...
Open console in Applications>Utilities, check the system log for the date/time of the last problem & the Startup right after that for clues.
Hello BDAqua, thanx for the suggestions. Before I saw this reply I tried to first quit the finder and then to relaunch the Finder but that resulted was a blank gray screen.
In the end I ended up having to power down the iMac.
Fortunately the RAID array that was "active" seems to be fine and also has a firewire 800 connection so I can use it_ just not with thunderbolt until this issue is solved.
I'm going to check in the Applications>Utilities>system log to see if any clues are evident_ thank you for the suggestion.
PS: Nothing of note was obvious as a root cause in the Activity Monitor though.
hmmm....I was told that the Helios and seritek card were compatable and that the Helios didn't require any drivers..it will be a drag if there isn't an easy fix for this since this new PCIe card from seritek is the first to offer port multiplier compatibility for eSATA to thunderbolt...since they are both new I'm hoping that an OS upgrade will be the fix (presently7.2)...we shall see.
BDAqua_ there's that saying... " don't fix it if it ain't broke"_ well, it appears there is something to that, at least in some ways.
I'll come back again_ if and hopefully when I find a fix for this_ to share with you and others cuz I'm sure there will be other folks who may come across this same issue as they "migrate" (haha) from their older Mac Pros to newer iMacs... I guess there isn't enough people out there who need 12 cores for Apple to really address a new Mac Pro...but you'd think the hollywood business alone would be buying enough of them to make the effort worthwhile.
I don't really need 12 cores, as I'm not editing 4K video in real time_ at least most of the time so have been replacing the MacPros that have moved into retirement with new iMacs.I just keep the high res files on hand and edit with 2K and the high end iMacs seem to be handling that just fine.
Until we meet again...