In a recent security patch (MS15-48), Microsoft® made a change to .Net security which affects the calendar controls in the NextGen® Practice Management and EHR products. This causes the calendar control to throw an error to the end user. Microsoft is reviewing this change internally and they have provided NextGen Healthcare with a registry entry to work around the issue. NextGen Healthcare also is working to provide a hotfix for NextGen ambulatory versions 5.8 UD2 and 5.8 UD1 to resolve the calendar control. This change will affect all supported versions of NextGen ambulatory products.
If you experience the issue and have not rolled back to a previous version of .Net, please contact Support for the registry entry to resolve this issue. The problem number for this issue is 59307, and is published under Known Issues.