user geting another user login name and info after he loged in with his own username and password

Hi,

we encountered a problem recently.Some of our users sent us email indicating when they login to the system after a while or when they refreshed the page, they saw someone's else login and info.For example user1@test.com logs into the system, he goes to his dashbord and select where to go, after a while when he refreshes the page, he sees user2@test.com   on top of the page.We use &APP_USER. and Appex 3.02 and our own authentication scheme which simply checks the validity of user .

I tried to look at monitoring log and I obsereved that