iPhone disappears from My Computer after selecting "trust this computer"?

Hi,

I'd like to access my photos on my laptop for transferring. When I connect my iPhone to my laptop with the USB cable, it registers under My Computer, but when I open the DCIM folder, it's empty. The "trust this computer?" pop-up appears on my phone and when I select trust, the iPhone just disappears from My Computer! This happens every single time, and I tried many times... 😟 I've never had this problem before; the last time I did it (quite a while ago), I was able to open up DCIM and copy out my photos without issue.

I'm using a Windows 7 Home Premium 32-bit OS, and an iPhone 4s with iOS 7.0.4 installed. It works perfectly fine on iTunes (I can update, backup, sync, etc).

Any help would be appreciated, thanks!