Help Calendar notification sounds - inconsistent

[maxrelaxn]

I've searched around the forums but haven't found this yet. Has anyone noticed on their Incredible that the calendar notification sounds don't work? This is an inconsistent problem for me...sometimes the sound will turn on and other times it won't. The notification LED works though. Here are my settings:

Calendar - Exchange
Settings > Sound&Display > Notification Sound > Subtle
Settings > Sound&Display > Ringer Volume > Use Incoming Call Volume For Notifications is checked
Ringer Volume is set to somewhere in the middle

I've tried changing the Notification Sound to something else to no avail. Please help. I don't want to miss my appointments