After debugging this issue and working with Microsoft, we have finally resolved it on Share Point 2010.
It is not consistent but happens much more frequently on “Calendar list”. This is a very typical error occurs in Share Point 2007 for asynchronous event handler. If you still have save conflict issues like we did, in Share Point 2010, we have the option to make these kind of events Synchronous by adding this in the file of the event receiver while we are registering it.
Due to Share Point and the event receiver code trying to update the item at the same time.
Conditional formatting has always been a pain point in Share Point 2013 and Share Point Online (Office 365).
Especially for those working with Share Point 20 where you were able to do conditional formatting using Share Point Designer.
SPWeb Event Receiver Asynchronous Events Share Point Foundation 2010 New Events Microsoft added several new events to Share Point Foundation 2010 on Site, List and Item level.