First thing to check would be the version of JET.
Locate msjet40.dll (typically in windows\system32.)
Right-click and choose Properties.
On the Version tab, you see the major version (4), and the minor version
(should start with 8 or 9, depending on your o/s.), e.g.:
4.0.8106.0
If the minor version starts with a number less than 8, get the patch from:
http://support.microsoft.com/kb/239114
Next possibility is a difference in locale.
Open the Windows Control Panel.
Under Regional Settings, what differences are there?
You can actually minimize the differences in regional settings if you
declare your non-text parameters, and typecast your calculated query fields
as described here:
http://allenbrowne.com/ser-45.html
and handle your dates like this:
http://allenbrowne.com/ser-36.html
Another option is the setting under:
Tools | Options | General | Database sort order
If the query uses VBA functions, another possibility is differences in
library references:
http://allenbrowne.com/ser-38.html
Next, is the possiblility that Access is confused about the names used in
the query. Name AutoCorrect can do that:
http://allenbrowne.com/bug-03.html
So can using reserved words as field/table names:
http://allenbrowne.com/AppIssueBadWord.html
If you're still stuck, post the SQL statement that yields different results.