Every time I save or edit a calendar entry, the up and down data arrows come up for a second. I'm wondering if the calendar entries are being saved on BlackBerry's servers or something?
I had this problem, posted to this and several other boards and received to helpful reply. It was so annoying, because every time I added or changed a calendar entry, I had to wait at least five seconds.
Finally, I figured out what was causing it, at least for me.
I had installed Google Sync. Even though I had it "unchecked", i.e. not to perform the sync, it still caused the apparent network activity. Since I wasn't using it, as soon as I uninstalled it, the behavior went away.