Since Starting Strength treated you so well and you made such good progress, I'd surely listen to the guy that got you this far in such a short period of time. You are now an Intermediate lifter and need a routine that serves such people. Mark Rippetoe, the creator of Starting Strength, has a great intermediate routine that is made for guys in your exact situation. Here is what Mr. Rippetoe has to say. . .
"The fact is, it's necessary to subject the body to increasing amounts of stress at a level that challenges recovery ability so that the adaptations continue to occur. But since these are now higher-intensity efforts that more fully tax the system, they require longer periods of time to recover from.
If we design the program correctly, we can plan workouts that place optimum stress in the optimum pattern to continue the adaptive drive of the program for a long time: A high level of tonnage-stress early in the week, a lighter workout in the middle to aid in recovery — "active rest" it's sometimes called — and then a higher-intensity lower-volume workout at the end of the week.
Stresses of different types and adequate recovery from the stress are in balance if the program is to work for an extended period of time. We call the program The Texas Method, because we are in Texas and it's a Method — a very good one that has proven itself for years." - Mark Rippetoe
What he's saying is that your squat is strong enough now that your recovery ability can't keep up with squatting three times a week. To continue to squat heavy three times a week will cause further stalls and even regression. Don't keep banging your head against the wall, it's time to use the Heavy/Medium/Light method and keep that progress moving forward. It's NOT a change of routine, it's a more complex progression plan that you are ready for.