I have a HP M1530 printer working fine on Windows 7. I get the error the handle is invalid after I update .Net framework to V4.0. I tried to install latest printer driver, still no luck. Any ideas? Thanks.
There were .Net framework incompatibilities with Windows XP for certain versions. This is the first I've heard with Windows 7. Try rolling back to the previous version (or just uninstall V4.0). If that fixes it, you will probably want to hide updates pushing V4.0 so you don't inadvertently recreate the problem.
It is production environment, I can't roll it back. Let's assume the issue is due to .Net framework incompatibilities with win7 or printer driver. How to make it work. However .Net 4.0 works well on other Win7 computers. So I think maybe .Net 4.0 has incompatibility issue with printer driver(HP M1530)? but I already installed latest printer driver and no luck.
Even in a production environment, you should be able to do a 5 minute test of uninstalling, testing, and reinstalling. You really want to confirm what the problem is before you spend a lot of time exploring solutions in the wrong direction.
If you are sure the problem is with the printer driver, try contacting HP tech support. You would not be the only person with this incompatibility and they might have a fix.