It is maybe a dum question but I don't understand...

I have a packaged application that is running in North-America. I now have a Russian company using it in the USA and they need to enter Cyrilic information in the fields (memo, etc...) to show when they send their invoices and other document to Russian companies.
When they enter it it does not keep it correctly.
For example, copy & paste Добро пожаловат will give something like ÄÎaôî....

Any clue ?

Many thanks
Eric