Media types are calling it the "Oxygen virus." When Oxygen President Geoff Darby announced via internal e-mail that the startup women's network's had canceled two shows, someone forwarded the e-memo to a well-targeted list of reporters, editors and competitors. An embarrassed Oxygen executive said, "That's the last cancellation notice going out on internal e-mail." For the record, gone are Trackers, an afternoon block aimed at teen girls, and Pure Oxygen, the primary prime time block. Both are going into repeats for the summer because money's tight. One insider counts 28 people out of work.