ronenmalka,
Sorry that you ran into this issue.
Can you answer some more questions for me to understand the issue better?
1) How did you install ME 9.0 ? Is it through Pulse / All-In-One Installer / Archived Update site ?
2) When do you see the error ? Is it during a save on a particular file ?
3) Copy paste the entire error from .log file which is located at <workspace dir>/.metadata/.log here.
4) Here are a couple of threads which discuss this issue. Can you please have a look at them and give the solution mentioned a try ?
https://www.genuitec.com/forums/topic/background-indexer-crash-recovery/
https://www.genuitec.com/forums/topic/backround-indexer-crash-recovery/
Let me know how this works for you.