I have a problem which requires I regularly restart my iMac, up to several times a day, to get devices recognized.
When I re-connect a device, iPhone, iPad or iPod, I regularly get the message:
iTunes could not connect to this iPhone. This device is no longer connected.
They no longer show up as active devices in XCode.
When I plug a phone in, it asks me to confirm it should
Trust this Computer but that doesn't make any difference.
Note that this is on re-connection. The devices are fine up until the point when I disconnect them. That doesn't change whether I "eject" them from iTunes or not.
Modal nature of problem
It seems that after this problem has started occurring, plugging any new devices in suffers a similar problem.
The problem survived a system restore from backup, which returned some 50GB of space to me. It originally showed up in Mavericks and I have since done an in-place upgrade to Yosemite. It's a mid-2011 iMac 21.5" with four USB ports.
The problem occurs regardless of whether the devices are connected directly into a USB port on the iMac or via the keyboard's extra ports. The devices are all getting power and show up on the System Report as being connected, eg:
USB2.0 Hub: Product ID: 0x0608 Vendor ID: 0x05e3 (Genesys Logic, Inc.) Version: 77.60 Speed: Up to 480 Mb/sec Location ID: 0xfd140000 / 6 Current Available (mA): 500 Current Required (mA): 100 iPhone: Product ID: 0x12a8 Vendor ID: 0x05ac (Apple Inc.) Version: 7.01 Serial Number: 52c05c8223d3efc793f2815e9d3dbcc018805880 Speed: Up to 480 Mb/sec Manufacturer: Apple Inc. Location ID: 0xfd143000 / 10 Current Available (mA): 500 Current Required (mA): 500