When you try to open QuickBooks, you see this error message:
This error usually occurs when a QuickBooks system file has been damaged or cannot be found. This can sometimes occur when an antivirus has incorrectly marked a QuickBooks system file as being infected with a virus.
On August 15, 2014, Avast! antivirus incorrectly flagged the DMUSERS.DLL QuickBooks file as being infected and quarantined the file. This will cause this error to occur.
Solution 1: Perform an Avast Virus Definition and Program Update:
Solution 2: Check your antivirus program for files that have been quarantined.
Click here for steps on checking quarantined files in Avast! antivirus.
For directions for other antivirus programs, please consult your Anti-virus help documentation. NOTE: Intuit recommends you contact an IT professional before making any edits to your anti-virus programs.
Solution 3: Perform a clean install of QuickBooks