I think I discovered another issue, related to the memory leak. My site application throws here and there the following error:
 gzcompress() [function.gzcompress]: insufficient memory (@line 204 in file /var/myndweb/common/framework/TViewStateManager.php).
#1 TViewStateManager.php:204 -- pradoErrorHandler(...)
#2 TViewStateManager.php:204 -- gzcompress(...)
#3 TPage.php:374 -- TViewStateManager->encode(...)
#4 TPage.php:957 -- AllUsers->savePageStateToPersistenceMedium(...)
#5 TApplication.php:481 -- AllUsers->execute()
#6 index.php:27 -- TApplication->run()
A restart of the server allows to resolve the issue, but only temporary. I'm using the LSAPI.
This behavior is not spotted in Apache.
The suggestion to restart the server seems interesting, but won't it destory the server side sessions, and will cause a mess with the applications?