With BP 1.7 RC1, there is a problem with the activity update when "attach media" is enabled. Two textares are overlapping.
Setting the BP textarea to "hidden" lets one update the activity and attach media, but I loose the ability the BP textarea provieds, such as @autosuggest.
Hiding the BP Media textarea brings back that, but won't let me send activity updates and displays the Attach Media button wierd.
I don't know what they changed in RC1, but it seems to be broken since that update.