[Freeswitch-users] Read only filesystem

I certainly don't know if this is a freeswitch specific issue, but we have several systems in the field running freeswitch on top of CentOS 5.5 and others on Ubuntu 10.04. Some of the systems, after a weeks of performance, go into a read only state on the hard drive, at which point, a restart is the only fix. After the reboot, the drive seems OK - I've run smartctl to verify that all seems good. Sometimes, in readonly mode, it even gives an I/O error when trying to execute the /sbin/shutdown and we have to manually reboot. At this point, I am trying to figure out what may be the root cause. Has anyone else experienced something this? Any suggestions? Thanks, Troy