Vlookup ~ formatng

I make quite extensive use of Vlookup & Pivot tables. Sometimes I run into problems when the LOOKUP cell and the table are not formated (i think)the same.
To clarify, I get a ‘n/a’ response in the formula, but when i copy and and paste the lookup cell to the table (or the other way around), the formula work. I have tried formating the lookup column the same as the table column i.e. text or number but it does not seen to work. This gives me a headache specially when the lookup cell is within a pivot table.
suggestions pls !!!!!