internet tethering and mms cannot live together

[jpma]

hi all
I've got iphone 3gs,

successfully got internet tethering working by the benm.help
and mms works too.
just that it cannot work together.

once I use benm.help to set my internet tethering.
restart my phone then went into the apt setting trying to set the mms.
the MMS APN, Username, Password was overwrite by the Internet APN, Username, Password.

So once I set the mms, it will remove the internet tethering setting causes it to stop working, ending mms working but no more tethering.

is there anyway to fix this?
I'm not using AT&T