Laptop won't recognise iPhone?

Ok, so I plug in my iPhone 4S into my Acer laptop (both around a year old and working fine) and the little jingle for insertion into USB port sounds, but that's all that happens. The phone doesn't start charging, nor does the computer recognise that anything's been plugged in (I've checked the 'Computer' folder, nothing's there). Fairly sure it's not the phone - I plugged it into my mum's computer and it worked just fine - iTunes recognised it was there and opened immediately, and that's what my own laptop did until about a week ago. I've also tried plugging in my USB hard drive (it transfers files just fine) and my old 2006 4GB iPod nano (it charges and transfers music fine too).It just seems to be the iPhone 4S that my laptop doesn't like. Any thoughts on how I can fix this? Just to clarify: My laptop recognised everything I plugged into it a week ago, now it recognises everything else EXCEPT my iPhone! It was fine, now it's not.

When I open up the properties it says this:
"Windows can't verify the digital signature for the drivers required for this device. A recent hardware or software change might have installed a file that is signed incorrectly or damaged, or that might be malicious software from an unknown source. (Code 52)" The only software/hardware change I'm aware of is updating to iOS 6.0.1 and updating to the latest version of iTunes, but iTunes recognises everything else I plug in, and when I plug the phone into my mum's computer it runs fine, like I said.

Bow Ties:

Shut down your machine (completely) and then plug in your phone into a free USB port. Power on the machine and see if your phone's charging status stays the same or whether or not it notices the connection.

* In some cases, ANY usb connection with a phone from a power source too weak to charge it will ignore it completely; both DATA as well as CHARGE.

Once you're at your desktop, look inside My Computer and see if the phone's showing up as a drive there. IF NOT, click START and RIGHT CLICK on the word Computer (or right click on My Computer if Vista or older) and select PROPERTIES.

Win7+ select the menu that shows "Device Manager" to the left.
WinV and older, choose the Device Manager tab.

Within the Device Manager, see if you have items listed as OTHER DEVICES or ones showing a yellow triangle. If so, drivers are needed for your version of Windows to see the phone correctly. ***this is likely as iOS update may have changed USB mode from "MASS STORAGE" which any Windows can see to things like PHOTO MODE, CAMERA MODE and others - even my Android updates have done this in the past few months and driver installs were required to fix the problem.)

Hope this helps lead you into the right direction!

PS: As for the "Supermarket": Tread with caution; if you confront him or attempt to be more than friends, you'll be in line with his other casual friends and expected to share.