I also have the same problem and I’m not hosting on bluehost or godaddy, ‘mail from’ plugin does not seem to fix the issue.
I use the ‘configure SMTP’ plugin for all three wordpress sites on this same hosting accout, all work except for the one where BP is installed. I believe this to be a BP issue since the problem follows BP, not the hosting company which hosts the WP/BP installs.
WP 3.0.1 and BP 126.96.36.199
update: uninstalled ‘configure smtp’ plugin, installed ‘WP-Mail-SMTP’, and ‘mail from’ = success! I hope this helps someone else too!