[CentOS] weird XFS problem

> Nevertheless, it seems to me that you should have more than 3GB of RAM
> on a 64 bit system...
> Since the width of the binary word is 64 bit in this case, 3GB
> correspond to 1.5GB on a 32 bit system...
> If you have a 64 bit system you should give it space to work properly.

... and the fact that a reboot seems to fix the problem could also point 
in that direction.