In IE10 Internet Explorer Maintenance GPO extension is no longer supported and the settings you previously used with IE8 are not correctly applied. The best workaround I could come up with is to set the following three group policy preferences for the user:
HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings
ProxyEnable REG_DWORD 00000001
ProxyServer REG_SZ 192.68.0.0:8080
ProxyOverride server;<local>