When looking to get help, provide a bit more info than "it keeps saying something about _____"...
Like exactly what it says, and what says it.
Preferably add the steps you took in trying to get it to work.
But basically, there's two ROMs... Bahamut's and Xenophobia's.
Xenophobia (XPA)'s is 'broken', but easily fixed.
Bahamut's is the same as XPA's fixed version.
Since XPA screwed up their dump, then went on to bash Bahamut in their 'fix', I'll be explaining how to use the patch on Bahamut's version. If you want to use XPA's version, just replace the download and ROM with the ones from XPA.
1). Grab your Bahamut ROM (Will not link, against ToS).
2). Grab the Bahamut patch: http://filetrip.net/f8673-Phantasy-Star-O-...-Patch-1-0.html
3). Open the RAR file (WinRAR, 7Zip or WinZip) and Extract the folder to your desktop.
4). Rename your ROM to "b-ps0.nds" and place it in the patch folder.
5). Run "b-ps0c.bat" and go grab a drink. By the time you get back, you should be done.
6). Rename "b-ps0-cracked.nds" to whatever you want and then copy it to your card.