broken 135 L

Just recently I noticed a focusing problem with my 135 L. It is lightning fast when focusing from near to far, i.e: focusing at 6 feet then focusing at 30 feet. But the reverse is when focus starts getting jittery. When I press the * (cf 4-1) when focusing from far to near, it starts to jitter. Meaning, it will focus a little,then stop focusing, or kinda vibrate like its trying to focus. I keep pressing the * button (about 2 to 4 times) till it focuses. Firstly, its only one way. Meaning I will focus at 4 feet then focus at any distance after 4 feet and it will be lightning fast, as usual. And when focusing near-by, meaning in the vicinity of 3~10 feet, it will focus back and forth perfectly. But it gets jittery when I have focused real far out ( I have not calculated after what focus distance it gets jittery when trying to focus closer). Secondly, its happening with this lens only. Other lenses are fine.
I did a little test, I focused at infiniti or close to that,then attempted to focus to 5 feet, it kinda hung and displayed the above symptoms. So I manually adjusted focus to around 5 feet or somewhere in that vicinity and it focuses fast. So in a nutshell,focusing closely, i.e: 3 to 6 feet it focuses fast,when I focus far out (more than say 15 feet), it jitters and hangs.

Any idea whats going on? I bought it about 6 months ago from a FM member. Not accusing the seller of anything because it worked perfectly for 6 months. Just letting people know I did not buy it new.

thanks!

That's just wierd. I was going to say check to make sure you don't have your AF set to AF servo, but you said all the other lenses work fine and this doesn't occur at certain distances. Send it to Canon for evaluation. Sounds like you might have a problem with your USM.

Nope, ive tested it a few times. Hoping the problem would just "go away" the next time I try to use the lens. Nope, still there. Actually good idea Lord Malone, im going to test it via AI Servo and see if it has trouble focusing from far to near.

Move vigorous testing results with the following:

Takes 3 presses of * to focus to close quarters. I can focus closely and normally in a radius of about 3 to 5 feet(rough calculations). After that -focusing further- it will begin to hang when trying to focus closer. Works the same way (rather doesnt work) in AI Servo.

Corrupted,
Hopefully it is only dirty contacts on your lens. Good luck with a solution. I know how important this lens is in the kit.

pturton, thanks for the support I love this lens. Works splendidly with a 2x TC. Also good call. Ill try cleaning or visually inspecting the contacts myself!