Audacity cannot play OGG files in the right way

I tested both files with the same version of audacity on amd64.

Both files sounds equal and I can't reproduce any of your problems. This indicates a driver problem somewhere in the audio stack (portaudio, pulseaudio, alsa).

I have similar CPU. But it could be a performance problem; I run many applications at once and I have many browser windows open (and there are flash, etc, etc). And I noticed that when I play OGG file in audacity before it is fully loaded (audio graphics is fully displayed), I hear more glitches. Once I see full graphics audio, I hear glitches only close to the end of the track.

I don't see audio problems in other applications (well, there are several bugs but in general, I don't have audio problems with my HW configuration; motherboard is GIGABYTE GA-MA780G-UD3H, AMD X2 5400+, 8GB of fast DDR2 RAM, audio is on-board, ATI RS780 Azalia )

Could you try to create some load on your PC and retry the test? I will retest on idle PC.
I understand you even cannot see that end of OGG playback is shifted against end of graphical representation of audio data. Correct?

One more point. In the case there is a problem in my audio stack, why Audacity can play FLAC without issue and I observe issue only in OGG playback??

I did more tests:
1) When my PC is idle, I don't see problem, Audacity plays OGG files OK.
2) When my PC is not idle (I run BOINC cloinet, so my PC is never idle but has always load with low priority), I see problem with Audacity and OGG files under this condition.
3) When I load file in safe mode (copy), OGG is played without issue (I cannot replicate the issue)

I noticed today once, that only one of OGG channels was shifted in time. One channel (left?) finished in time but right channel was played when waveform displayed silence.
I noticed today that channels were not synchronized (like right channel was delayed after left channel, it sounds like an echo.)

To replicate the issue:
1) run PC with some load, it can be BOINC client or some benchmark, or something else.
2) open OGG file in Audacity in fast mode (direct play from file)
3) play the file and hear the music, watch volume level indicator. Music sample should have at last 2 minutes. Longer sample has higer chance to trigger the issue.