Overwriting of cells/last number that survive....

[KJ_Ferk]

Hi
My problem is that content in Excel cells are "overwritten" by the last digit/letter I write.
Ex. I would like to write 123 in the cell, but the cell only shows the last digit I type, 3 in this example.
Same if I write letters, if I write Revenue, only e will survive and show in the cell.
It is also impossible to insert any kind of formulas in the sheet.

Have I "activated" by accident any function the result in this? Is it any virus? I don't know, but I am happy for any possible solutions......

[#2]

That is something I have never seen. The INSERT key will switch to a mode in which Excel overwrites values rather than inserting them into a string, but it overwrites the next character it encounters, not the one it has just input.