256, 512, 1024, 2048. I tried with these, but they all present the same problem, so, i don't think the problem is the buffersize. I use with Cubase and works fine. The problem is the Ableton with Fireface UC. Ah, im using the last driver version, Fireface driver_usb_win_1099, and firmware 123 (Hardware revision). I have another audio card, a Presonus Audiobox 22. With audiobox Ableton works fine like Cubase 5. Any other idea? And thanx for trying to help me.

You mean turn off (EDIT:) "Hyperhreading" in the BIOS ?

ramses and MC. Thanx to come to my post. I'm talking about the thing i did in Ableton. In Ableton you can choose Multicore/Multiprocessor ON or OFF. Nothing about RME or something out the Ableton. I know about many possibilities to try to fix the glitches problems but this thing, turn off Multicore/Multiprocessor, really fix it. Again, thanx for all. Hope other guys with the same problem could fix this kind of issue.

Ramses, thank you again. Exactly! The last thing is, i don't know why presonus audiobox woks fine with this option turned on in Ableton. The fact is. Works. But i don't use audiobox to record. Fireface is much better. I only use audiobox in my reharsals, and Fireface still in my homestudio. Usually using with Cubase 5. Anyway, now it's fixed. Hope my post could help others having a same problem. Best!

Hi, Ramses. I will try some upgrades mentionated, although the Bios i did last month.I don't think the problem is the quality of my usb cables. I have a lot and tested all. What i have: Vostro notebook, 3560. 4 USB ports (three 2.0 and one 3.1 super speed) i5 3th generation) 8 GB ram Corsair. Win Pro 7 (but not SP1) hd 1 TB 7.200 rpm. The USB card link i can't use. Notebook here. Anyway, i will do a Dell test about all in this note. Best!!!!!!