Rated 5 out of 5 stars

Great tool, But I've encountered a issue. I just tried Fx 17b4 to check it out, then went back to my usual install of 16, but now the newtab page is blank. not even any thumbnail frames when newtabtool is enabled. I can still enable/disable the panel at the bottom, but to restore a functional newtab, I have to disable newtabtools which obviously leaves me with hardly any quick launchers. I've checked about:config, and the correct values for rows/columns are present.I've removed & re-installed and also installed the dev version, results are still the same. any suggestions?

Edit:
Thanks Geoff, that did the trick :)

This review is for a previous version of the add-on (4.1). 

Remove browser.newtabpage.columns and browser.newtabpage.rows in about:config.