For one user, one Clarity project or program won't open in Microsoft Project (MSP) intermittently or it takes a long time to open. It hangs on the opening XML step. The below error message is then seen when trying to open the project after the issue occurs:

"The last time you opened <project> it caused a serious error. Do you want to open it again"?

Release : 15.6

Component : CLARITY MICROSOFT PROJECT (MSP)

1. Check to ensure the user’s MSP New Driver, MSP Version, and MSP Project Updates, Framework are all compatible with the Clarity PPM version.
2. Check to see if the there are any other differences between the user with the user with the issue and other users (IE VPN, office location,  machine setup)
3. See if increasing the java memory limit to 800 using the steps in KB: Set the maximum java memory usage for the MSP Interface helps
4. Reimaging may also help to remove the symptoms 
5. If no issues are found to point to root cause, please contact Broadcom support.

Reference: MSP Error: "The last time you opened 'ProjectID' it caused a serious error..." when attempting to open a project from Clarity

If the above doesn't solve your issue, see the following KB: MSP opening projects issues - master KB 

For other related MSP issues:

• MSP Integration Known Defects - Master KB
• MSP Integration Known Issues - Master KB