It's probably dropped into read-only mode at the LVM level (
lvs will lack a 'w' in the second caracter of the
Attr column), so you might be able to flick it back with an
lvchange --ignorelockingfailure -p w VolGroup00/LogVol00. Alternately, the VG may have dropped write access (typically caused by a hardware failure), in this case indicated by a lack of
w in the first character of the
Attr column in the output of
vgs. That can't be changed at runtime, by the look of it.
If LVM has dropped write perms on either the LV or VG, it's probably for a very, very good reason, and unless you care not for your data, I'd be looking into the root cause rather than trying to bludgeon LVM into allowing writes again.