Yes for me something similar.
For the past 3-4 days I can intermittently sign in, even make a single post, (I only usually inhabit the traditional forum), but as soon as I start to navigate away from the page I was on the site logs me off. I then can't log back in.
Sometimes, but only intermittently, if I close my browser then go back to BF (which I've just done to post this) I can sign back in but then experience the same problems all over.
I initially thought it was because I'm close the to re-registration date for my Basic Membership which is around this time, but I don't think that's the case.
The few multi-quotes I've tried (in the trad' forum) have resulted in me being logged off.
I contacted BF using the contact icon at the top right of the page but without response but I'm sure their a busy lot so please don't anyone take that as a criticism.
Hope someone can sort this out.