Not an answer but to confirm similar problems in 2003.
When I try to merge numbers into a Word mail merge doc.
the numbers will add several decimals. I have tried
pasting values into Excel and the round function with no
luck. What I do, which works, is copy and paste the
worksheet to a word doc which dumps the data into a table
then merge the Word table to the Word mail merge main
doc. It's an extra step but it gets the results.

the data does not show up.  A "0" appears.  I have
formatted the Excel field as General, Number, and Text
with the same results.  Also, when a field is blank,
the "0" appears in the Word document field.  I've never
had this problem before.  

See Empty cell in Excel for a possible answer.

the data does not show up.  A "0" appears.  I have
formatted the Excel field as General, Number, and Text
with the same results.  Also, when a field is blank,
the "0" appears in the Word document field.  I've never
had this problem before.