I'm posting this one because I found my own answer to an annoying situation and didn't find this same problem listed elsewhere. Hope it helps someone else.
Our 2005 Legacy sedan was in at my (previously) trusted oil change place. The battery was 5 years old, at the bottom of the marginal rating, we live in Minnesota and they had a good price on a good battery = new battery. They promised they had the right equipment to keep a small charge so I wouldn't have to reset the ECM. When I started it up, not only were the radio pre-sets gone, I had a rough engine and a solid check engine light - You can guess I wasn't happy.
I did the ECM reset, but the check engine light wouldn't clear. I took it to an auto parts place and they couldn't get a reading from the Data Link Connector / ODII. I called my local dealer to get the location of the fuse they might have blown and was told there are no fuses related to the ODII - Bring it in and the will run it through a full diagnostic $$$. Well, I'm not a sucker (there are/should be fuses protecting all electrical equipment) so I spent the evening with the schematics (bought a pdf of the repair manual from subarumanuals on ebay a while back) and traced down some possibilities. MB13 (7.5 fuse in the motor compartment, far right side of the fuse bank, 3rd from the bottom) was blown. Replaced it and all is well.
My guess is they ran too much juice through their little gizmo - So my new question is did they have the choice of power settings and mess up or is it unusual for this to be on a little 7.5 amp fuse... Don't know, but their (lack of) response to their screw-up has me back making appointments for oil changes at the local shop.