I have Super Street Fighter 4 + Arcade Edition DLC and all costumes. My friend has Super Street Fighter 4. We are trying to play against each other, but when I receive an invite, I can't join in his session and when I send an invite, he receives a message that tells that he needs to download something. As far as I know, the problem is not with the costumes DLC, since I already played against a lot of people that does not have alternate costumes. He tried to download and install the Update Kit for SSFIV, but the problem continues. I tried to change the version of my game, but the problem continues too. Do you know what we are doing wrong? Is it impossible to play with two different versions? I'm asking this because in the network battle I have an option to play against SSFIV only. I almost forgot. We are using PS3.
I solved the problem. My friend SSFIV version is European. His psn user is american. When he downloaded the update kit, he did using the american ps store and the update kit is for the american version of SSFIV and even this package being installed, it does not changed his game (european version). Thinking about this, I said him to create an european psn account, access the european ps store and download the update kit. The european update kit worked as expected and now we are finally able to play.
If you had access to the exact error message, that would likely help narrow down the cause, obviously. But failing that, here are a couple of ideas for things that might be happening:
There are two things that may possibly be happening:
And as you have said, the costumes DLC does not affect this in any way whatsoever.
EDIT: Here are some pictures of the lobby settings that I mentioned in item #2.
Select "SSFIV" on the options menu when you create a new Endless Battle lobby. (I'm not sure whether you could even pick "SSFIV AE" if you didn't have AE installed, but it's worth checking in any case.)
When you create the lobby, the host should see the silver SSFIV logo in the lower-left corner of the screen. (Gold signifies AE, while gold and silver signifies the "both" option.)
If the host is following these steps and can verify that only the silver logo is shown, then I'm afraid I don't have an answer for you. Posting the exact content of the error message that's generated would be the next place I'd go to find an answer.