Let's face it. Any Office Suite program is quite a complex beast. And has had programming and development since the mid 90's or earlier. The problem is, that often, Microsoft Office gurus, whether they may be Em Vee Pee or not, think they know most facets and features well. Except that we don't. Know the program well enough.
Take this basic spreadsheet example.
Start up Excel. Any version - take your pick - '97, 2000, 2002/XP, 2003 or 2007
Type 1 in A1
Type 2 in B1
Type =A1+B1 in C1
Simple formula, right?
Copy C1 from this worksheet (probably Sheet1) to A1 on Sheet2. You should get a #REF! error. That's as expected - you've copied a formula to another sheet without copying the precedent cells.
Switch back to Sheet1 and select A1 and C1 neglecting B1 - (you do know about selecting non-contiguous blocks?)
Switch to Sheet2 and Paste with cursor on A1. What do you get? Well, you get the 1 as a value A1 and you get the 3 as value in B1. The 3 is not a formula, it has been converted automatically into a value to save you work.