Reporting Services - Excel vs HTML ERROR plz help

Hey,
I have a little format issue with Excel 2003:
I am working in reporting services - creating a report. The SQL store
procedure returns a date with the following format:
MM/DD/YYYY HH:MM PM/AM
In my report on that perticular text field I have the following format:
dd/mm/yyyy HH:MM:SS
Because I want it in military time.
It displays fine in the report but when I open it in Excel it brings up
the following ERROR:
"File Error. Some number formats may have been lost"
And it shows the date columns the following way:
"38692.46597"
The document is NOT huge and does't contain more than 2000 rows.
Any ideas on how to solve this?
Sorry for posting twice(first post on here).
I have put this same post in the reporting services group.. Sorry