This is actually a registry issue. In my experience it usually is associated with malware. Typically it is only a residual problem left over since this class of malware is normally easily detected and removed.
I am not sure how qtcore4.dll factored into it but it seems to be an important system file.
If you think it could be corruption Click here
for Microsoft's solution.
Also, run some hard drive diagnostics and checkdsk
Malware is more likely...
I couldn't find the article to link but Microsoft published a statement on technet that said after an infection is removed the system has still been permanently compromised.
What this means: Assuming proper removal there is nothing actively malicious on your system, however, often malware creates system vulnerabilities. While active they can flag your IP to a remote server for future intrusion.
Microsoft's solution? - System re-imaging.
Bottom line: System files don't get corrupted without a reason, check your rig.