Odd thing happening with forum topic post notifications

Hi,

I have an odd thing happening - not sure if it's something to do with the customisations I've made so confirmation would also help.

If I have notifications set for a group - then if someone else posts a topic (or replies etc), the notification I receive is from the 'group' not the 'user'. That is, in my elgg inbox, rather than having the subject preceded with the user icon and name, it's preceded with the group icon and name. Further, if I try to reply to it, I get the system error message "We could not find the recipient in the user database".

If it's down to my customisations, any thoughts on what I might have done?

Thanks