Translating the data in the Location Bar into a web address is the job of DNS servers - perhaps yours changed. A switch of service providers will (usually) result in a change in DNS server.
For both IE and FF, if you're going to a .com address, just type the domain name into the Location Bar, e.g., computerhope, and use CTRL+ENTER.
There are other key combinations: SHIFT + ENTER = .net address; CTRL + SHIFT + ENTER = .org address.
Hope this helps.