Setting "Recipients -> Remote lists" produces 403 error

I have mlm set up fine. I've got lists set up, can access them via lm.php, run commands in browser, can do 'diagnose' and 'get info' fine, so everything working well and looking good ... until I choose "remote lists" from "Recipients"

and I just get this
Error #403: Forbidden ( ... **&lang=us)

('XXX' is not actual domain name!)

How can that fail? I run it in the browser and it works fine.

So currently I have everything set up but can't send any emails out.

Can I send you URL privately ? Don't want list in public forum and start getting spammed or other nonsense.
It must be a permission thing right?

Here is what diagnose shows my permissions as:

mailqueue permissions = 0755
sqlqueue permissions = 0755
uploads permissions = 0777
imports permissions = 0755
templates permissions = 0755

Is there something in there which means the dB is accessible from browser page using password in URL, but not from inside MaxBulk program itself?
Can you at least give me an idea how you are trying to access the DB from inside maxbulk?

The puzzling thing is the DB is perfectly accessible from your 'diagnosis' and 'get info' pages from within MaxBulk, and also perfectly accessible from within the web browser.

Doesn't that suggest to you the DB is actually well set up ???

Give me some help here. If I go to my web host, and I say the DB is diagnosing as 100% successful and 100% accessible from web browser, they are tell me the function in the program is bugged and bounce me straight back to you .....

Please, give me some real support on this. What SQL commands are u running in maxbulk when 'recipients -> Remote lists' is selected.

Thank you very much
Update: I just went back into MaxBulk and selected "Remote Lists" and it actually worked properly :) I have changed nothing in DB setup in the last two weeks.

So no idea what has been wrong for the last two weeks, but most likely there is a bug in MaxBulk which stops remote lists from being accessible sometimes. There is nothing wrong with the DB setup, even MaxBulk 'diagnosis' confirms that fact.
I think I have worked out when the error occurs.

Its when I am using the MLM web interface to delete lists etc

THEN I go into MaxBulk and select "Remote Lists" - it produces the 403 error

If I don't have the web interface running concurrently everything is fine.