“After installing Service Pack 2 for ArcGIS Desktop 9.3.1, opening a map document from Windows Explorer, ArcCatalog, Windows Desktop, Windows Recent Documents, or the Web does not open it in a new ArcMap session. That is, if you open an existing map document, ArcMap opens as expected. However, if you now open another map document, it will not start a new instance of ArcMap. Instead, the map document is sent to the existing instance.
This is a known issue. For updates on the status, you can use bug number NIM059009. Esri is working on a permanent solution to this issue. In the meantime, please use the following workaround:
1. Run C:\Program Files\Common Files\ArcGIS\bin\ArcGISFileHandler.exe.
2. Under Map Options, it should show ‘Open in new application’ as being checked. Change this to ‘Open in running application’.
3. Click OK to close the ArcGIS File Handler application.
4. Run C:\Program Files\Common Files\ArcGIS\bin\ArcGISFileHandler.exe again.
5. Under Map Options, select ‘Open in new application’.
6. Click OK to close the ArcGIS File Handler application.
Map documents should now open correctly.
Esri apologizes for any inconveniece this may have caused you.”
From the ESRI Support Center News Blog:
“After installing Service Pack 2 for ArcGIS Desktop 9.3.1, opening a map document from Windows Explorer, ArcCatalog, Windows Desktop, Windows Recent Documents, or the Web does not open it in a new ArcMap session. That is, if you open an existing map document, ArcMap opens as expected. However, if you now open another map document, it will not start a new instance of ArcMap. Instead, the map document is sent to the existing instance.
This is a known issue. For updates on the status, you can use bug number NIM059009. Esri is working on a permanent solution to this issue. In the meantime, please use the following workaround:
1. Run C:\Program Files\Common Files\ArcGIS\bin\ArcGISFileHandler.exe.
2. Under Map Options, it should show ‘Open in new application’ as being checked. Change this to ‘Open in running application’.
3. Click OK to close the ArcGIS File Handler application.
4. Run C:\Program Files\Common Files\ArcGIS\bin\ArcGISFileHandler.exe again.
5. Under Map Options, select ‘Open in new application’.
6. Click OK to close the ArcGIS File Handler application.
Map documents should now open correctly.
Esri apologizes for any inconveniece this may have caused you.”