High load on the server. The operations hang or it takes too long to execute.
Identify the exact domain causing high CPU load: open IIS > server_name > IIS > Worker Processes. Depending on the result, apply one of the following:
If the issue is caused by application pool exclusively used by Plesk, please, contact Parallels Technical Support, as additional investigation is required.
If the issue is caused by application pool of a client's website, the case falls out of Parallels Technical support scope . It is recommended to contact system administrator regarding the issue.
Limit CPU usage for application pool of the domain, following instructions from the article .