This sounds like more of a mental "meltdown" than a physical issue. My mental game in terms of putting has gotten much better lately. One thing that has been working very, very well for me lately is to visualize in my head the putter flying into the basket exactly as I am hoping to putt it. It is kind of like a mini-movie. Sometimes I may replay the movie a few times. If I don't feel like the line I am imagining is a good one, I will step back and figure out a better line (usually higher or lower). If I am visualizing the putt well, I can usually throw a decent putt, regardless of whether it sticks or not.
The second thing is definitely having a consistent routine. Even more importantly, your estimation of how well you are putting should be centered around whether or not you are executing your routine, NOT whether or not you are making putts. If you are doing your routine you are probably going to be putting confidently (assuming you have a routine you are confident in).
I played a round today and putted great. Some putts were high, some were low, but I followed my routine and, despite all of my putts not going in, stayed positive and did not let the misses affect my play. I hope this helps.
E* DD2, Wraith, Glow Firebird, S-P-C PD, TD, Leopard, Roc, KC Aviar