If you can't get online with Browser A, but can with Browser B... that is a huge warning sign. Uninstalling and reinstalling is probably just resetting some options that have been changed by you accidentally or possibly by malware of some sort. Simply switching to a new browser is ignoring the problem.
There are a million reasons one browser might not be able to get online. But here is a really quick method to try and fix IE.
1. Use IE 8. If you aren't up to date, you are asking for trouble.
2. Go to Tools -> Internet Options -> Advanced -> Reset Internet Options
3. Go to Tools -> Internet Options -> Security -> Click Internet Globe -> Reset All Zones to Default Levels