Thanks for the follow-up and for sharing your solution in forums. This will certainly be useful for other developers as well.

I investigated that further and found out something interesting in the ScriptManager docs, which might explain this.

One key difference exists in how the ScriptManager treats scripts retrieved from the filesystem compared with those embedded as a resource in a dll. When the path to a script is used, the ScriptManager provides a callback to the ScriptResource handler, which retrieves the contents. The script itself is not modified (no extra calls are injected). When a script is retrieved as an embedded resource, however, the ScriptManager injects the call to Sys.Application.notifyScriptLoaded for you automatically. This allows you to start using scripts that you already have with ASP.NET AJAX without having to rebuild the dlls.

...

So, the way I see it, in the first case the scripts were used from the embedded resources (this is the default option) via WebResource.axd, and in this case ScriptManager automatically added notifyScriptLoaded for us, hence no problems in your scenario (making an initially invisible control visible with UpdatePanel). By default our controls use the javascript embedded in the assembly (not ig_common).

In the second case, no embedded resources are used and the problem you get is related to that.

I guess it is a rare case to not use default resources + the combination to show controls with ajax updates - hence we were not able to detect that so far. I guess, the solution here is to have the notfiyScriptLoaded() call in all cases in the files we ship originally. I will suggest that to the development team.

Hopefully this is not a major showstopper for you currently. 

Hi Rumen,

Thank you for your suggestions, but I can't use absolute paths like "~/JS/NetAdvantage..."  because the app is always going to be deployed in a virtual directory which name will vary so it has to be relative. That works for me anyway.

I have resolved my problem - it was a valid AJAX script exception. Here I'll add my two cents as they say:

REASON: This is to do with the fact that after partial page postbacks scrips load asynchronously and then we need to notify Sys.Application that the script has been loaded and parsed. (This relates only to the ASP.NET AJAX Toolkit framework)

SOLUTION: Adding the following script at the end of every Infragistics script file loaded on that page fixed my problem.

if(typeof(Sys) !== "undefined" && typeof(Sys.Application) !== "undefined")

Sys.Application.notifyScriptLoaded();