Help Computer doesn't see my phone!

[Sorinari]

I've had my phone for almost 3 months now. I've used my USB cable to charge it, work with HTC Sync and access its files as a USB storage device through the "disk drive" option. Now when I plug in the phone, it charges but does nothing else. The icon at the top of the screen in the notifications bar doesn't appear saying it's connected to a computer in any way. The computer doesn't say I have something plugged in. And when I go to My Computer, the drive doesn't show up where it usually does, or at all, for that matter. I've tried turning my computer off and on. I've turned my phone off and on. I've removed the battery and put it back in after 10 seconds, also done the same with my SD card. All of these multiple times. I know my USB cable is working because my phone charges. When I have the phone disconnected from the USB cable, but the cable plugged into the computer, the computer says there's an unknown device plugged into the USB drive. However, when I plug the phone into the cable, the message goes away and nothing happens but the phone charging.
I have no idea what happened or why it happened now after working for so long. Please help.

 

[tpbklake]

I've had my phone for almost 3 months now. I've used my USB cable to charge it, work with HTC Sync and access its files as a USB storage device through the "disk drive" option. Now when I plug in the phone, it charges but does nothing else. The icon at the top of the screen in the notifications bar doesn't appear saying it's connected to a computer in any way. The computer doesn't say I have something plugged in. And when I go to My Computer, the drive doesn't show up where it usually does, or at all, for that matter. I've tried turning my computer off and on. I've turned my phone off and on. I've removed the battery and put it back in after 10 seconds, also done the same with my SD card. All of these multiple times. I know my USB cable is working because my phone charges. When I have the phone disconnected from the USB cable, but the cable plugged into the computer, the computer says there's an unknown device plugged into the USB drive. However, when I plug the phone into the cable, the message goes away and nothing happens but the phone charging.
I have no idea what happened or why it happened now after working for so long. Please help.

Go into Settings -> Connect to PC and make sure that the "Ask me" box is checked. If that box is not checked and the "Default connection type" is set to "Charge only" then your phone will behave as you describe.

 

[Sorinari]

I had that box unchecked because I almost always use it as a disk drive. When I usually plug it in, it doesn't ask me and goes straight to using the disk drive function. However, the icon in the notification bar that looks like a little USB symbol still shows, which I can drag down and tap to open the change functions menu so that I may switch to charge only or HTC Sync. Even if I don't have it ask me, that little notification is always there. It's not now. I tried toggling the "Ask Me" box, but it did nothing. I don't know what else to do.

 

[Mr. Ed]

Have you recently installed any syncing apps like doubletwist? They typically have a setting in their menu for autosync...that overrides the stock connection manager. In my case doubleteist was forcing the phone into usb mode and would not allow me to change it. Uninstalled doubletwist and problem has been gone since.