Notification Panel

[Bob]

Why do icons "fall" into Past Items and no longer appear
in the Notification Panel? Eg:power icon (I am using a
laptop)
I have found by doing a full scan at reboot some icons
come back to the Active Items and are visible but not
necessarily, and in any case, not necessarily for longer
than the PC is on.
Could this have to do with using only 124Mb memory? I have
ordered 256Mb but am waiting...
Thanks for any help,
I have spent hours on the knowledge base.
Bob