We find that sometime this error may occur when EM cache went out of sync with APMDB.
Release : 10.7.0
Component : Introscope
Can you please take the following steps and see if this helps.
1- Stop WebView and MOM Enterprise Manager processes
2- Delete the entire content [all files and directories] of [EM-Home]/work and [WV-Home]/work folders
3- Delete the entire content [all files and directories] of /configuration folder except file config.ini (DO NOT delete config.ini file)
4- Delete the entire content of <EM-Home>/logs and <WV-Home>/logs
5- start MOM Enterprise Manager and WebView processes
Note: If Enterprise Manager and WebView are installed under same directory, then [EM-Home] and [WV-Home] are the same.