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