I have an ASP.NET 4.0 app developed in VS 2010 with several working Crystal Reports. With my latest report creation, I made a copy of an existing report, modified it by adding some sub-reports in the group footer and report footer, and verified that it runs properly locally in VS. However, when I deployed it to the web server, it would just hang forever with no report viewer ever appearing on the page. After testing other report modifications with and without sub-reports and not encountering any issues, I returned to the problem report and now I always get the infamous error message, "Load Report Failed". Restarting IIS and even rebooting the web server have had no effect.
I've run out of ideas of things to check. It's a fairly complex report and I really don't want to recreate it from scratch, but I have in the past run into cases where doing exactly this inexplicably fixed my problems.