It is possible that McAfee could be the reason why you are experiencing this issue.
You could uninstall, then reinstall McAfee to see if that solves the problem.
If you decide to take this approach, after uninstalling from Add Remove, use the
McAfee Consumer Products Removal tool
before reinstalling. The tool will (supposedly) remove any traces left behind.
If a reinstall doesn't solve the problem, it could be a case of McAfee just not playing nice with your system.
Of course, there are other reasons why your browsers are slow to open but since you mentioned McAfee I am addressing that question.