I have been login in from different computers, only my laptop can talk to SoundMondo, and my music PC has to many MIDI drivers. :-)
Today I was unable to log in to the forum, but I could log in to SoundMondo on the PC and the laptop. After trying a lot of times and getting no response, being logged out when changing pages and even an error from ".NET", I changed the pasword(via the Soundmondo user account), but still was unable to log in to the forum.
In a desperate attempt to restart the connection to the page, I deleted all cookies from yamahasynt.com and this worked, as you can see.
Please look at the cookie handling and see if you can find the root of my problem, now that the solution is known. Perhaps connecting from different computers at the same time, is part of the problem.