I cannot connect my LG GU280f mobile phone to my computer to download photos

Un-install off any possible programs of the phone , then reconnect to see if the phone is detected. If not there are errors in the PC . Now remove the memory card and use a adapter to place into the card reader as you can check the images , and scan the card for any possible errors. After downloading format the card and reinstall necessary files.
Also you can try to use Blue-tooth to connect the phone and PC , activate and link together and then transfer images.

Maybe you won't have to... If the phone has a memory card, and you find a card reader, what it takes is to move everything from the phone memory to the card, shut down the phone, move the card to the USB card reader and copy everything from the card, in your computer. Nothing easier...