I can no longer click on thumbnails to show posts
As the title suggests.
I have tried the solution in another post but it did not work for me.
I logout, clear the cookie and login, nothing happens
I tried the view posts method, I am already in view posts mode
If you have tried that then I don't know.
I had that problem about 2 times in the past long ago on a different PC.
I had to clear everything the first time. Try to clear your whole history:

Firefox example:

History > Clear Recent History...
"Clear All History" Window:
Set "Time range to clear" to Everything, check every box and click "Clear Now".

If that fails and you're really desperate, you could try to re-install your browser to a clean state.
That worked for me the second time. That route sucks though since all your preferences are gone and you have to re-install whatever customization options you had for the browser.