Aggregate device problem

Hi, I've been using Logic 7 on my Intel Core Mac OSX 10.4.11... (i know!!!) and it's been great until recently!! I like it, and don't want to upgrade yet.

I've been using the Aggregate device to combine my Focusrite Liquid Saffire 56 and Mackie Onyx 1620... great! I've recorded many drum tracks with no problem what so ever.

Last year my hard drive went, got it replaced. Since then... my Aggregate Device doesn't work as smoothly! The Focusrite works great on it's own (no AggDevice), as does the Onyx.... but when I combine both using AggDevice the secondary interface (Onyx) goes bananas! All sorts of issues from latency to bit crushing sounds! While the primary interface (Focusrite) works fine. e.g. recording drums, I need 10 tracks.... so 1st 8 tracks on Focusrite then 2 tracks extra on Onyx.... the 2 Onyx tracks go crazy while the Focusrite tracks are fine.

Is there a remedy?! Appreciate the help.