Yes, the reason why your meta trader is hanging is because it's trying to load so many bars in it's history. It's usually okya when you have a low number of charts open, but when you have a large number open each of which have so many bars that it's trying to load, it becomes a soft memory and cpu nightmare. The computer can't handle it and often times meta trader will crash almost immediately.
Maybe try to close some of the chart windows immediately after you open meta trader before it starts to hang, or try to change the number of bars in the history if you can access the options menu.
There may be a way to delete the number of charts open without opening up meta trader but I'm not sure how to that. Maybe you go into the profiles section of your meta trader and delete the current profile (move it out of the folder for safe keeping reference).
As a last resort, you could back up the most important templates, indicators and expert advisors in your meta trader folder; uninstall meta trader and then install it again.
I hope this helps, at least some what.
Markets can remain irrational longer than you can remain solvent.