I already posted the question actually (Linux Mint 17.2 suddenly loses write access to filesystem), but since it occurs rarely I need to ask again with some new info I gathered.
I suspect that this error somehow related to cron activities and/or audio card driver. Every time it happens, one of the last entries in logs is about cron and today there was some about audio driver. Here it is:
12/22/15 10:17:01 AM duat-re-P55A-UD3 CRON[2824] (root) CMD ( cd /
&& run-parts –report /etc/cron.hourly)12/22/15 10:17:34
AM duat-re-P55A-UD3 pulseaudio[2501] [alsa-sink-ctxfi] alsa-sink.c:
ALSA woke us up to write new data to the device, but there was
actually nothing to write!12/22/15 10:17:34
AM duat-re-P55A-UD3 pulseaudio[2501] [alsa-sink-ctxfi] alsa-sink.c:
Most likely this is a bug in the ALSA driver ‘snd_ctxfi’. Please
report this issue to the ALSA developers.12/22/15 10:17:34
AM duat-re-P55A-UD3 pulseaudio[2501] [alsa-sink-ctxfi] alsa-sink.c: We
were woken up with POLLOUT set — however a subsequent snd_pcm_avail()
returned 0 or another value < min_avail.
So can somebody guess what should I do to get rid of this error?