The problem occurs when a custom extension which includes the Database Access extension as a dependency is created and the custom extension's install script attempts to make an SDE connection. If the attempt is unsuccessful, the custom extension is unloaded, but the Database Access extension is not. Typically, when a custom extension is unloaded, any dependent extensions should also be unloaded.
A dependency on the Database Access extension is created whether an SDE connection is made or not.
theSDEConnection = nil
theExt = Extension.Find("C:\esri\av_gis30\arcview\ext32\dbaccess.avx".AsFilename)
If using this option, it is important to place this code within the "If...then" statement that checks for the SDE connection.