what cpu and what ram? what video card? what version of firefox?
generally speaking one of the problems with installing ubuntu within windows is it will use more resources than normal to run things. This could be the problem but without knowing your system, its just a guess at this time.
generally speaking one of the problems with installing ubuntu within windows is it will use more resources than normal to run things. This could be the problem but without knowing your system, its just a guess at this time.