To resolve the issue, either set the English System Locale in Region and Language options or change the decimal separator setting in Region and Language > Formats > Additional settings > Decimal symbol (for Win 2k3: Region and Language Options > Regional Options > Customize > Decimal Symbol).
Make sure you change the decimal symbol for nworks collector service account.
Next, trigger full topology rebuild in nworks UI > Enterprise Manager > Rebuild Full Topology (available, when the Enterprise Manager node is selected in the left pane). Once the topology is updated, the issue will be resolved.