Each domain you send mail from needs to have an SPF record that includes all servers that may send mail for that domain.
If your setup is that mail from yyyyyyyy.com can originate either from google apps or the server foo.xxxxxxxx.com, then it seems like you want an SPF record in the yyyyyyyy.com zone that looks something like one of these:
Code:
v=spf1 a:foo.xxxxxxxx.com include:_spf.google.com ~all
v=spf1 ip4:a.b.c.d include:_spf.google.com ~all
Where a.b.c.d is the IP address of your server.
If you also send mail from the xxxxxxxx.com domain, then you need another SPF record for that zone.
And stick with the ~all until you get everything working right - once you are comfortable you can switch to -all if you want.
Can't help much more if you are going to keep the real details secret.