This situation only happens on limesurvey server have no right to access internet.

There is a config calls 『comfort_update_server_url』

add to the config.php and leave it blank then problem fixed

this is interesting.
To be sure that I understood well what you're saying :
Once you updated to the last version, your LimeSurvey became very slow. Then you understood that it was because it had no access to internet, and removing the comfort_update_server_url resolves the problem. I'm right ?

In the next release, LimeSurvey will check for new update only once a day, so it should not be a problem anymore.

you got my points. thanks man.