This might be a problem related to the java VM space usage being maxed out and not being freed as needed. I think this is suposed to be resolved in version 2.5.x. We are having the same issue at my workplace and we tempoarily fixed this by increasing the size of the VM. Unfortunately, the problem still exists, but increasing the size gives us more up-time and we can restart each morning before users start logging on. This can be done by adding the a file called vmoptions in the bin directory with the following lines:
where the 64 is the min VM size used and 128 is the max VM sized used.
We used 256 for both min and max for about 50-75 users and it allows us to go one full day with no problems.
(PS I think there are other posts regarding this that might be more helpful…)