Does your RPi freeze?

[JD Patxiku]

I have a 512mb Raspberry connected via Wi-Fi to my NAS.

I have modify cache buffer size on advancedsettings.xml and it does not seem to work, I've checked on the logfile and advancedsettings.xml loads. After reading some threads I decided to create a swap on my SD and when I check if it is working it doesnt. (Now I have no advancedsettings.xml or swap).
When I try to play HD movies on my RPi it freezes and then stops, buffers some time and it plays again but this does not take long.
I have checked this thread and observed that people is not having problems with video streams. I'm using NFS for streams.
Does anyone have a WI-FI connected RPi working without freezes?
I was wondering if "saving" the cache on a USB device or a SD card is possible.