The Project Connector for Connections Online 4.0 (COL) has a known bug that we are in the process of fixing. The bug is that tasks in MS Project may inadvertently be marked "dirty" (which means it has been changed since last sync) due to patterns in selecting tasks in MS Project or by inserting a Column in the MS Project view. The Connector sends "dirty" tasks to COL and they will overwrite changes that have been made in COL since the last synchronization. This bug occurs if you add a new column to a view or you click on the same row twice.
To workaround this, users can display the Flag20 Column in MS Project. This is done by right-clicking the column bar at the top of the view and selecting Flag20 or by using the Add New Column option in MS Project 2010.
If this field is marked "Yes", it means that task/resource/assignment will be sent back to COL and will overwrite COL changes on the next Synchronization. If the user wishes not to send this item back to COL, they should change the Flag20 column value to "No" for each item they don't want to synchronize. Please note that if the Task has assignments, the Flag20 field must be set to "No" for all assignments and the task itself to prevent overwrite.
This bug is current as of 5/24/2011. We expect it to be resolved in the next release.