It's kinda har to say (up_OARaiserror looks like something custom made) other than xp_sendmail is generally a royal PITA to get working. From when I used to use it, I can't recall the need of any sp_OA* procs.
Probably the 'easiest' (?) would be to get rid of xp_sendmail altogether - use xpsmtp instead.
http://www.sqldev.net/xp/xpsmtp.htm
It's easier, more reliable, and... just works. I recommend at least you take a look.
/Kenneth