i believe this is Yosemite. I have a late 2009 8gb, SSD mac Mini, and had the same issues... the problems became worse for me, effecting all AV sources. Luckily, I had just upgraded to an SSD with Mavericks, and then CC cloned from my old hdd.
i wrote the following about a month ago...Hope this helps.
In a seemingly unrelated problem, If I tried to save a photo out of a browser, download an app, etc.. The access to disks was dog slow.
Further, I had the well known Wifi problem reported all over the web.
These problems persisted even after the latest update to 10.10.1
I have an SSD with Yosemite on it, but I had recently CCCd from a spinning mac drive which was Mavericks. Then I updated the SSD to Yosemite.
As a Sanity check, I rebooted from the old spinning mac drive into Mavericks, and just like magic, my chronic problems disappeared! All of them!
I have since CCCd the SSD back to Mavericks, and my Mac Mini is now lightning fast... no exaggeration.
In my opinion, this is a software-hardware interface or I/O software issue, which affects all devices: Wifi, HDD, Sound, Video, Bluetooth, and anything else you may have attached. I also feel that this “fix” will be a long time coming due to its far-reaching nature.
Let me know if there is a fix, till then, Ill stick with Mavericks.