Different formats for size and location properties

I have created a program in C# that uses XML files to load controls. I use reflection to load and present the controls. This program is used on multiple Windows platforms in Europe and USA. After a Windows update in a computer in USA, it seems the format for Size and Location has changed. I've always used the format "32;32" to specify width and height. Location uses the same format to specify X and Y coordinates. Now suddenly the notation has changed on this single computer so it has to use the format "32,32", ie a comma instead of a semicolon. This relates to both Location and Size and any other property that takes multiple values. This means I have to change hundreds of settings to reflect the new format, or find out why the format changed. I suspect there's a setting in Windows to control this, but where can I find it?