Seems AT&T is having some issues with their release of 188.8.131.527 for the BlackBerry Bold. Boy Genius posted the following information regarding the pulling of the handheld OS upgrade although the information seems to be lacking full reasoning as to why exactly it was removed.
AT&T customers are simply being asked to wait until another release becomes available in "the near future", which with AT&T could be forever. Hard to even guess at the real reasoning for it, but for those of you who have already upgraded AT&T isn't at this time issuing any notifications to downgrade so--enjoy your visual voicemail if you have it. If you didn't update already you may be left waiting.