So I'm not too familiar with Linux and I began to use Ubuntu to get familiar with it, I'm using Ubuntu 12.04 and this problem began occurring when my tower fell over last night. I used to be able to open programs such as Skype, and run downloads however now it does not seem to work. I am getting no error messages, just nothing happens.
welcome to the askUbuntu forum. To be honest your question requires further description of the problem, so we can give you some valuable feedback.
Anyhow, I since you mentioned that your tower fall over, I would say that there is a chance that your hard disk was damaged. Especially if the PC was turned on at that moment.
To check your hard disk for any problems, you can use the 'Disk Utility' in Ubuntu.
Also you can force a file system check on the next reboot you perform.
Use the following command to do so. Note that this takes some time to complete.
Hope that helps :-)