OpenOffice from ODM to ODT

I've apparantly had another version of OpenOffice than the 1.9.125.1.2 i have now. At least I have some files saved in .odm format, whereas my current version calls them .odt. That wouldn't matter if it were able to read the odm files - but it can't :-( I've tried all possible filters. Unfortunately OOO doesn't tell me anything about why it won't read them; it just shows an empty document. I can see the contenct of the .odm files if I unzip them, so I know they aren't empty. My question is if there is a way to import the old documents into OpenOffice?