Validation problem in forms server only

[Gonçalo Boléo]

I design an expenses report and in forms server only i have a "little"
problem.
One of my fields is a calculated field (a sum of expenses) and in Infopath
Client application i don't have any problem.
In forms server mode i don't have any problem until i submit data. When i
submit it my calculated field shows an error of invalid data but only when i
have decimal places (it replaces the decimal separator period with comma and
for that reason the data became invalid).

In my develop environment i don't have this problem!
Could it be a regional settings server problem? Sharepoint configuration?

Thanks for your help,
Gonçalo Boléo
Portugal