Internet Explorer Proxy settings

Hi all I have a unique issue. On our network we have ie 4,5,and 5.5 clients with bordermanager 3.7 as a proxy. Randomly, the bypass proxy for local addresses and automatically detect settings are being checked. 5 or 6 clients per week are having this issue. I am not sure if it is a BM issue or some other unrelated issue any help would be appreciated