Excel not Permitting A Paste

[d_monkeyboy@yah]

Hi,
I am working with a Mac computer with Excel (version 11.4.1). I am cutting and pasting data from some previously typed cells as well as typing new data. Suddenly I cannot cut & paste or I cannot correct in any of the cells. I have to correctly type the data the first time or I have to start over---like the old typewriter days. If I try to type a letter anywhere in the cell it deletes the entire cells' data. I might have hit a set of keys that changed a preference, but I have no idea what, nor how to change this back.
Sound familiar to anyone?
Please help
Dan

[mikerickson]

Pressing ESC would be my first move, but if the problem has precisited after an entry is made in a cell, that probably won't work
Have you tried Saving, that fixes things sometimes when Excel gets weird on my Mac.
Does SavingAs give you a working file?
Are any of the sheets protected?

Does this affect all your workbooks or just this one problem child?

(Mac OS10.5 Excel2004)

[d_monkeyboy@yah]

Thanks for responding. It seemed to only happen in certain cells. I carefully typed my data and moved on. I tried copying & pasting in other cells and it worked fine. When I returned to test the original cell---it still was a problem. I tried duplicating the file and it still happened in the new one in the same cells. I did look through the preferences and the file is not locked. I couldn't tell looking through all of the preference tabs what settings could be off. I did try typing something in a cell (using the shortcut buttons) and I got colored numbers in brackets such as [34]+[35]... but they were in colors. That is the only other strange thing happening at the same time.
I'm over my problem---but I expect it to happen again. So, my trust in Excel has diminished.
Any more ideas would be welcome
Thanks
Dan