Is this a Multi language site?
Can you check out this entry in web.config?
< add name="DNNFriendlyUrl" type="DotNetNuke.Services.Url.FriendlyUrl.DNNFriendlyUrlProvider, DotNetNuke.HttpModules" includePageName="true" regexMatch="[^a-zA-Z0-9 _-]" urlFormat="advanced" />
The urlFormat should be advanced.