It's good to know you found the answer.
One other thing which you might or might not already know about, if you go into the worksheet properties in the VB editor you can set the EnableSelection property to 1-xlUnlockedCells which, when the worksheet is protected, will only allow unlocked cells to be selected. If you unlock your "tabbing" cells you will then be able to move through them by pressing either Return or Enter, or still use Tab if you prefer. No other cells can be selected though.
I found this in the forum recently when I had a similar problem to yours. In Office 2000 which we use at work this setting kept turning off everytime I closed the workbook so I made an autoexecute sub-routine turn it on when the sheet was activated.
Good luck.