HELP!!! Arduino IDE will not start!!

Hi All,

I am new to microprocessors, but not to loading programs or extracting files from Zip or Tar folders. The problem I have I've never seen before, three days ago I loaded the Arduino software onto my PC and ran it until just a couple of hours ago..NO Problems.
Today, I tried to load a library from GitHub? and had problems so I tried a different library from another site and the IDE GUI froze. The Arduino program would not open so I uninstalled it, rebooted my PC and reinstalled it. Still Will Not Open!

Help, I do not know how to proceed and I am in the middle of an important project build, can anyone help me?

PC running Win7 64bit with lots of RAM and lots of HDD space.

HI All,
Solved the problem, now everything is normal again. The problem was

What was the problem?

Kindly describe the solution so that others can find it helpful too.
Glad that the issue has been fixed.