Read the orthodoxwiki article. Both claimed to be the official church both claimed Russia had given them permission, and that they were officially the real church. There was legal dispute over properties, which was a problem ROCOR had everywhere especially after 1991 when the status of teh MP church was globally recognized again and countries started giving ROCOR proprties back to Moscow (a big reason for their warming up of relations with Moscow being they stood to lose access to what had been ROCOR churches and historic places for almost a hundered years.
ROCOR and the OCA both claimed to be separate from Moscow in 1917, and both were part of the Moscow church prior to that, one being the church which came to America through the purchase of Alaska, and the other being the missionary church.
Here's the OCA official version:
http://www.oca.org/MVhistoryintroOCA.asp?SID=1
Here's the ROCOR official version:
http://www.russianorthodoxchurch.ws/english/pages/history/briefhistory.html
The orthodox wiki article seems the least biased.
Until 1991 there was at least a good reason to be wary of the MP and thus the 1970 communion with the OCA; the large presence of the KGB hand in the Moscow church (most of whom haven't exactly left btw).
At this point however the Russian FSB (The KGB no longer exists) has shown less enthusiasm with church operations it had, though I wouldn't say the Moscow church operates completely outside of politics either.
That said the OCA churches are nothing like Russian churches. I've been to church in Russia and ROCOR churches are darned near identical (though smaller in design at least the ones I've seen). It makes sense for the ROCOR to be in communion with the MP.
Also
http://www.russianorthodoxchurch.ws/01newstucture/pagesen/news05/fifthcomm.html
http://www.russianorthodoxchurch.ws/01newstucture/pagesen/news05/mpbeslan.html
Most of the posts I've seen online regarding the OCA and ROCOR try to make them seem 'unofficial' churches, always with the goal of proping up something they are doing.
Considering that the schism in 1054 was mostly do to the bishop of Rome trying to institute a policy that the Roman Bishop and Rome itself were more official than other churches it seems ridiculous to me that any churches would attack another on that basis.
"Considering that the schism in 1054 was mostly do to the bishop of Rome trying to institute a policy that the Roman Bishop and Rome itself were more official than other churches it seems ridiculous to me that any churches would attack another on that basis."
You've lost me....Who's attacking whom?