If you do go through with this OP, be sure to save any worlds and mods to another spot so they are not lost. To do this, go to "%appdata%" and the .minecraft file will be there. Copy any worlds or mods you need to a safe place, then delete the ".minecraft" file. To create a new ".minecraft" file, simply open the Minecraft launcher. This does usually fix the issue, however there may be another way. Perhaps try using a different version? It may be an issue with the profile you are using also. (By profile, I mean 1.8, 1.7.2, Forge, etc.)
Your profile can be found here:
(This isn't my screenshot, I found it on the internet.)
