BrawlBox - Not enough storage is available to process this command.

Hello.
First of all, I'll admit that I'm quite new to Wii Game hacking, so hear me out.
I'm trying to hack the music in Rhythm Heaven Fever by modifying rev_tengoku.brsar (where audio is stored) but the problem is that every time I try save the file (no matter what change I make) I get an error that goes like this:

Not enough storage is available to process this command.
(Exception from HRESULT: 0x80070008)

I haven't done many tests, but it seems like only this one file used by RHF is getting BrawlBox to display this error message, because I've tried editing and saving other .brsar files and managed to do it with relative ease.
Anyone know what I could do to solve this problem? I would really appreciate it.

Thanks.