|The problem is not a BlueDragon one but rather a common problem that trips up even ASP.NET developers. If you set up your IIS 6 application pool to enable the "web garden" (or setting the "max number of processes" for that pool to greater than 1), you are in effect creating a cluster of instances.
A problem exists, however, if you enablel .NET sessions in BlueDragon's admin and also have left .NET's session management to its default of storing sessions in memory (inproc). The problem is that, now with web gardens enabled, if a user is moved by IIS and .NET from one process/instance to another, the session on the first won't exist on the second.
The simple solution is to change your .NET session configuration from "inproc" to either "stateserver" or "sqlserver". Again, this is purely a .NET problem with a .NET solution. It was discussed at further length in a BlueDragon blog entry.