Most likely there is something different about the values in B5 and
Temp!B5 that is preventing an exact match. Is B5 formatted as a
number, and Temp!B5 is formatted as a string? It may be a leading or
trailing blank space, for instance, or one of the values may start with
an apostrophe(this usually happens when the value is imported from a
database or another application). You can test for this *using a
backed up copy of your data* copy copying the value in B5 to cell
Temp!B5. If the VLOOKUP returns the expected value then you'll need to
perform some secondary processing to remove the offending characters.

How did you print out the ascii code for each char in each string?
Just curious. Excel's CODE function, for instance, only returns the
ascii value for the first char in a cell.