CauseThis error may occurs if some of VE resources limits have been exceeded.
ResolutionFirst of all enter to the VE and find if any resources limits are exceeded by looking on User Beancounters. If failcnt for some resource is being increased, you can set this parameter limit to greater value using the vzctl command from the hardware node, for example the command for setting shared memory resource limit looks like
# vzctl set VEID --shmpages 8400:8400 --save
Where VEID have to be replaced with the real VE ID.
General Plesk resources requirements can be found in the corresponded FAQ article.