Looks like the may be a jpg file split in two, with a file splitter, or OE's own splitting option, Kitz E Kat. Have you tried Combine and Decode from the "Message" menu in OE? If not you'll have to ring your brother get him to re-send.
When a mac makes a directory for some files, it adds the .dat extension to an enclosing folder. I suspect that what you are picking up with this wierd looking file name is just the folder as designed by mac.
A long time ago, I had to do cross-platform work and I just learned to reject these .dat thingies.
No it was from a PC for sure,i got seven emails from the bro and the sister got two , with a weird error message....
This is mad!!!!
Now i open OE and the send/ receive tab is grayed out, i can't click on it..
I loaded up NAV 2004 and did a full scan but it found nothin, meanwhile my lapper is totally screwed up!!! So, on a prefectly working fully loaded up to date lapper, i download 'dodgy' files which have no virus, and more or less straight after the computer goes mad?????
My AVG has picked up a couple of Double extension files like yours and reported them as a virus, I removed one of the extensions, In your case ?.dat and [1-2]? leaving the file as a .jpg, it then worked ok.
I don?t know whether this is anything to do with your problem, but thought I would chuck this in, on the off chance it would help.