runtime error 13 type mismatch

hi,
im not too clued up on microsoft excel. Im running a macro that my boss has set up which takes data from a list and sorts it into alphabetical order. The macro works fine until I either add or remove data, then i get this error.
here is the macro.....

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someone please help!!!!!!!

like i said, i am not too clued up on excel so treat it like your talking to an idiot lol.

I just tried this and it seems to work fine for me. Runtime 13 is a type mismatch, what data are you adding?

Does Excel highlight a line in the code when the mismatch fires?

this is highlighted when i click debug....

If ActiveCell.Value = "" And Selection.EntireRow.Hidden = False Then

C'mon people, help!!!!!