Try another one! Recently, I ran into some hardcore malware that was undetectable when I used my normal favorite two removal tools: Malwarebytes and Superantispyware. Mostly, I run into this problem with root-kit malware that is apparently undetectable at times.
But then there is program called Hitman Pro 3.5 that I discovered recently which, no joke, found the root-kit within seconds of being launched. I sat there for 30-40 minutes with the other tools and they found nothing. Hitman pro 3.5 found the malware within seconds!!! I rebooted the device and problem was solved.
What I like about Hitman Pro is that there is an install option that allows you to just run it once. Since it is a free application (there is a paid version), running it once keeps you legal if you need to run it on multiple PCs for a business or company that will not spend money for a corporate license.
So the next time, you think you are out of options, get a second opinion from Hitman Pro.