The forum now uses a different, more effective, system of marking your threads read. The feature used to be cookie based, and is now directly marked within the database. This is generally a more accurate system, though it is resource intensive. Now that Specktra is on it's own server we have the resources to take advantage of this feature.
Did you know you can subscribe to threads and manage them within your userCP? It's a pretty nifty feature that is turned off by default, you can manage the options in your userCP. You can subscribe to threads you read automatically or you can choose to subscribe to them within the thread in the "Thread Tools" dropdown menu. HTHS!