I posted a little while ago about an odd 'Memory Leak' I was having...well, after several days of trawling (and annoying Data Wanta who's excellent email component I was mistakenly blaming - sorry!), I finally found the answer! Turns out that the little [STAThread] attribute above the main class of the Comand Line app isn't so inoccuous after all - Dave pointed out this thread - apparently there's some sort of bug in .NET  which can lead to what is effectively a leak when using multi-threading in a STAThreaded application!