I have also been running MODX on a couple of hosts over a period of about 4 years (I think) and all was running ok, until my current host (jumba hosting) switched the particular server I am on to cloud linux as a trial for their servers. I noticed the problem almost straight away, but I can only assume no other CMS platforms or web software has been affected as a few months later Jumba decided to update the rest of the servers to cloud linux and then another person on this thread (PAGALO) noticed his sites doing the same thing on Jumba servers. I don't pretend to understand server set ups, only limited knowledge from what I have gained during this experience. But it appears to me there is an issue with MODX and cloud linux (or maybe a particular version of, or setting in cloud linux)
I have once version of Revo installed on the server 2.0.4 pl2 and it is clunky. The resource tree pretty much fails to load every time I do something like update a resource, so I have to click the refresh button. But sometimes even the buttons underneath the tab are not even there, so I have to refresh the page. Some other times if I click on a resource to edit it, the loading circle will just hang in the middle of the screen and I have to refresh and try again.
So I am assuming the problems are related to the same server issue, but the different versions of Modx are displaying different behaviors.
I am really unsure what to do as a long term solution. It will be interesting to see if other people start buying into this thread who may be having the issue on other hosts.