Primavera P3.1 running on Windows XP SP3 issue

One client called me yesterday said his Primavera P3.1 suddenly had problem on the resources module since last month, and it worked fine before. I know P3.1 is a 16 bit application and it won't work in 64 bit system. But his issue for P3.1 was totally different, because only the resources linked to the activity had problem. The symptom is when you select an activity, and click on the Resources tab, and add/change resources for the activity, the entire P3.1 application was close without any warning. I reinstalled P3.1 without luck, and set P3.1 to run compatible with Windows 98 did not fixed. I concluded P3.1 conflicted with other applications running in the background, so I launch msconfig and disabled suspected background services, restarted the windows, and Ooh, the issue's gone! I took me almost 1.5 hours to resolve this problem.