Vista - Problem with Case-Sensitive fieldnames

I have a problem in my code when the fieldnames use diffferent casing
in an intgral datatable to an sql datatable.

This problem only appears to happen at the moment on Spanish PC's but
we cannot replicate the problem or identify why this might be
happening.

For example, the datatable may have a field called "ClientName" and
the sqlTable has the same definition but called "clientname".

When we write to the sql database, we use data-adapters and
parameterised Sql to stored procedures.

Can anyone please tell me why this is happening, why only on certain
PCs, if we can overcome this issue by turning on a switch or setting.

Thank you in advance for any feedback.