Multiple IF formulas

Hi,

I'm having trouble with a formula.
I have a spreadsheet that I run, to log overdue items by number of hours they are late by.
If the item I'm waiting on is overdue by 4 or more hours, then I want a statement to automatically populate in the "results cell", to say "4+ hours late". The same applies for items overdue by between 0.01minute and 2 hours, and between 2 hours and 4 hours, with corresponding statements (i.e. "between 2-3 hours late" and "up to 2 hours late").
All I want to have to do, is to log the time the item landed on my desk, and let the formula work out how late it is, and give the correct statement depending on how late.
I have therefore entered the following formula in order that the appropriate text be displayed depending on how overdue a particular item is:

=IF(D74>=C74+4, "4+ hours late", IF(D74>=C74+2, "2-3 hours late", IF(D74<=C74,"on time", IF(D74>=C74, "up to 2 hours late"))))

However, the formula is missing out the 2nd part of the IF formula (between 2-3 hours late). The 1st part works perfectly, as does the last part, but for anything that should be between 2-3 hours late, the formula is returning "4+ hours late" which is wrong.
Why is it skipping the 2nd part?

Please help!!

Thanks.