I have and older home that has knob and tube wiring going to a fuse box.Can I switch out the fuse box with a breaker box?Are there any problems with doing this?

Sure you can, and are probably long overdue, for upgrading to circuit breakers.

The K&T wiring will need to be junctioned at or near the panelboard over to Romex or some other wiring method that can be connected to the panel.

This will still leave all the K&T wiring thruout the home as is, without an equipment ground, yea I know, Captain Obvious, that's me.

Each existing circuit will need a 15 amp breaker, as I am sure all the K&T wiring is all #14.

Once the panel is changed out, then you can begin the process of re-wiring the home as much as possible or practical, over to new wiring that has an equipment ground.