I'm often getting the address blacklisted thingy too when logging in and posting a reply.
Sa login part minsan kahit mag delete ka na ng history, reopen ng browser is still shows up; walang choice dito but to keep retrying. Dun naman sa posting part, and workaround ko is just go back to the previous thread page by clicking the title link itself (located between the "post reply" area and "logout") then click on reply to post. Your message should go through now. Don't click on the BACK arrow of your browser, it's not gonna do you any good.
Btw, Im using my computer so Im not sure if my tip will work on mobile. Also, not really a 100% guaranteed fix but it helped me most of the time.