Hi Josh
Sorry about the issue preventing web maps from opening in ArcGIS Desktop 10. This is still a problem in 10.0 Service Pack 2. The fix for this issue (NIM065725) is on track for being released in 10.0 Service Pack 3 later this year. However, this won't provide direct support for all the different types of data found in a web map. It will support ArcGIS map services, ArcGIS image services and OGC WMS services in web maps but not web map layers based on uploaded shapefiles, CSV files, GPX files, KML network links, or note features. Support for this wider range of web map content is planned for the ArcGIS Desktop 10.1 release in Q1 2012.