Ok, according to Baldr's guide, I have moved to Planting a Stealth Virus. He claims it is low success, but you dont get jailed. Ive been at it it 2 days and not succeeded yet, but not been jailed. I do have the enhancer as well.
It's been many many years since I've ever done those. There wasn't a crime guide for me to go by when I did them. So, I would give it another day or so and if you don't start getting success with it, I would just drop back to your last crime for a couple days worth of more crimes. (Personally I would drop back now rather than waste the nerve.) Then come back to this one and try again for another couple days and see how you do. If you're successful stick with it. If not, drop back again. Just don't give up little guy. May the force be with you. (Y)
I ran into the exact same issue. I ended up sticking with Thorough Robberies and was planning on just trying a Stealth Virus every few days. I ended up hitting 30 NNB within less than a month and since hitting 30 I have no issues. My personal suggestion would be to go back to Thorough Robbery until 30 NNB, since it doesn't really seem much slower, and once you hit 30 you should be all good.
Personally I used Nash's guide which seems to be very accurate so far. It suggests to do stealth virus once you reach 25 NNB if you have a few merits/edu/federal judge perk in crime success. If you don't what I did was do a couple hundred more thorough robberies and then did stealth virus with no problem. My estimate is that I went a little less than half way to 30 NNB on thorough robberies. Then once you hit 30 NNB you should be able to start arson right away.