I am/was currently running UltraWebGrid.v7.1.20071.40 (I think). I applied the hotfix which installed 1071, then version 8.3 in order to trouble shoot a problem. (8.3 actually fixed my problem).
Since that point I am unable to open any of my production projects using the .40 control without getting all sorts of wierd errors which I know are related to the Infragistics product. Projects which don't have the grid control open fine. If I delete the grid control from the offending project and comment all control references, all other errors disappear.

I uninstalled version 8.3; which did not correct this issue.
I uninstalled version 7.1 Hotfix 1071; which did not correct this issue.
After I uninstalled the hot fix I still recieved a message saying there was an add-in (Infragistics) which was not found (obviously not everything was removed).
I pulled back the original source from our production control libraries and I'm still unable to open projects without errors.

Following is the first error in the log which is causing all the rest:
Could not load file or assembly 'Infragistics2.WebUI.UltraWebGrid.v7.1, Version=7.1.20071.40, Culture=neutral, PublicKeyToken=7dd5c3163f2cd0cb' or one of its dependencies. The system cannot find the file specified. C:\ADI\ADIADONIS\BAR106D\Web.config 30 
ASPX entry:
<%@ Register Assembly="Infragistics2.WebUI.UltraWebGrid.v7.1, Version=7.1.20071.40, Culture=neutral, PublicKeyToken=7dd5c3163f2cd0cb" Namespace="Infragistics.WebUI.UltraWebGrid" TagPrefix="igtbl" %>
Config entry:
<add assembly="Infragistics2.WebUI.UltraWebGrid.v7.1, Version=7.1.20071.40, Culture=neutral, PublicKeyToken=7DD5C3163F2CD0CB"/>
<add assembly="Infragistics2.WebUI.Shared.v7.1, Version=7.1.20071.40, Culture=neutral, PublicKeyToken=7DD5C3163F2CD0CB"/>

Please help!  There is no way I can keep all my production apps in our development and production environments in sink when a project upgrade procedure, re-compile, and publish to numerous servers is required.
Thanks
Vic