We have Keil C51 under NT 4.0. By applying 6.12 patch, we noticed a modification of the registry for another application : ClearCase. This happened twice. In one case, the patch was applied by a standard user. In the other case this happened for an administrator. Installing patches becomes really thrilling !
Further investigations show that applying the patch was not the cause of the problem. The problem was revealed when the patch was applied, that was all. Sorry for this alarming message.