Windows 7 64-bit, ESRI ArcGIS Explorer 1500 (2.0.0.1500), default map
Add Contents, GIS Service, server type WMS, Version (automatic), get error message: Failed to connect to http://127.0.0.1/cgi-bin/wms?
I have used MSCompanion 1.00.35 RC2 to create a MapServer (from either latest ms4w or FWTools) map file. This map file (served by Apache web server) is working with Quantum GIS 1.6.0 (as WMS layer).
ArcGIS Explorer does not like this map.
If I simplify the MapServer map file (by removing all non-WMS metadata) then ArcGIS Explorer can display my map.
This looks like a bug in ESRI ArcGIS explorer where the connection to a WMS server fails if the metadata is not pure WMS. Also the WMS metadata is not interpreted correctly anyway. For example the attribution (which is set correctly in the MapServer file and correctly decoded by Quantum GIS) is either ignored or incorrectly decoded by ArcGIS Explorer. The grouping is not very well handled: the "Add Service" GUI should allow selection of individual sub-layers (only displayed in the Layer Properties) as layers. The display is also incorrect: I have setup the map to use ED_1950_UTM_Zone_30N (epsg:23030) to display both UK and Norway North Sea data, but only the UK side turns up (the side covered by UTM 30N). All the data beyond (in zone 31N) is not displayed. The same map drawn by Quantum GIS shows all the data.