We would need to see some logs in order to have an idea of what may be going on with the computer.
First do the steps listed HERE but ignore step concerning Deckard Scanner and substitute instead HiJackThis.
Download HiJackThis
Do a full system scan with it and save the log.
Post back here with logs from Malwarebytes' Anti-Malware (MBA-M) and HiJackthis and then we can see what you may be dealing with, be sure to have MBA-M remove whatever it finds and then reboot the computer and run the HiJackThis scan.
Judy