Sorry for the delay in responding.....I truly do appreciate the help. I fear as we've dug into the situation we are finding more pain rather than less. ....to answer the actual question.....no, we don't have any hidden SSIDs on these.
We are finding this issue to be problematic on a number of types of machine/network cards and in two different sites. The common situation is that we are running Aruba IAPs in both places. The networks are using WPA2, though we've also tried open networks for testing. We have tried both Ubermix and vanilla versions of Ubuntu. We have also tried a variety of kernels, NetworkManager versions, and wpa_supplicant versions....and even a foray into using WICD instead of NM. Basically, it seems that connections that were solid under Ub 12.04 are less stable (at least in our situation) in anything more recent. It also seems more problematic if there is a dense AP environment. Watching logs on the client, it scans the network repeatedly and keeps saying that authentication timed out. ....even with open wifi. We've spent hours on the phone with Aruba TAC and have tried various scenarios to clean it up. We've also spent quite a bit of time looking around for possible solutions online. The frustrating aspect is that we don't have challenges with our Windows or OSX clients. We've even checked out the 14.10 beta to see if perhaps that fixes things and have also forced the version 2.3 of wpasupplicant........seems a bit better, but still some failures.
For the time being, we are using UM 1.x with Cinnamon in our most problematic situation and are hoping to find a resolution so we can move these units to UM 2.x. If anyone out there has seen something similar (and has a resolution) it would be great.
Thanks for all......sorry for the rambling reply.