hello,
just want to say, that i am having a similar problem. only with some differences.
i upgraded my older mac to ML recently, and OO (version 3.3) had no problem with the transition. no permission problems... odt files still open with OO. yay!
however, on my NEW mac which of course came with ML installed... i installed OO (version 3.3), since that's all i had on hand, and can't make it the default for opening .odt files, as mentioned by other users above.
one problem is, my issue might be solved easily if i had internet access, but i can't connect because of another problem w/ the new mac (ie, java SE 6 not having come installed on the new mac - actually seems to be an issue with ML because that happened with the upgrade to ML on my old mac as well - and is the reason that i can't install my usb modem on my new mac, urgh!).
i checked out all the suggestions above, and none have worked. for instance:
>>get info>>open with>>open office>>change all... just bounces back to textedit and does nothing.
>>security&privacy>>general>>allow applications downloaded from... anywhere is selected... i had already changed that.
>>right click>>open with>>oo... well, that's all fine, but i want to NOT have to tell it to do that EVERY. time.
>>right click>>open with>>other...>>open office>>check - always open with... this is for this document ONLY.
so. my last idea is to download OO 3.4.1 onto my older mac (that has internet connection), transfer via EHD to my new obstinate mac, and HOPE it works... i'll report back when i'm all done with that.
VERY annoying because, i absolutely adore OO, and use it CONSTANTLY. i will be quite distressed if this turns out to be an irresolvable issue.