When launching ArcMap with the German locale using comma as decimal delimiter and adding a WMS service, the scale for the WMS service layers is calculated incorrectly.
This is an issue with ArcMap's support of WMS 1.3. If you connect to the WMS service and choose to connect to version 1.1.1 (available in the connection dialog in ArcGIS 9.3 only) this issue can be avoided.