some of my drawings have lost the abilty to snap even when i have the esaps on why would this be?

Type SETESNAP and check your settings. Entity snaps can be toggled on/off individually or as a group.

I have noticed that the snapping system works better without the mouse: just writing the initials (int, perp, etc...) or with a digitizing tablet which is what I use.

The entity snaps toolbar just sets on and off the modes. It works different from AutoCAD one, because ACAD's toolbar sets the snap mode in a temporal mode and overrides the other settings until the command is executed. Then, the settings return the way it was set.

What I've done is a new toolbar with temporal snap modes, when I just need a center and only a center snap, or anyone. It made me work more comfortably, and faster than typing the initials. If anyone is interested, I cand send it.

Here is what I did to the snaps:
From the pull down tool bar go to: View -> Toolbars... Then select "customise"
After this I select one of the snap buttons from the toolbar which is already opened.
Notice the bottom of the dialog box which says "command".
For example select the endpoint snap button.
Command says '_ENDPOINT
Remove the '
Now command says _ENDPOINT

Do this to each snap.
Select close.

Now the snap will work differently.
During a command the snap will be a one time snap.
Select the snap before a command and it will be a running snap.