(My own access is on and off, and when I manage to get through, LJ is painfully slow for me.)
This is their official explanation on their Facebook page:
"LiveJournal is currently up, but you may encounter some problems while attempting to use the service. Specifically, some pages may load slowly, the site may not respond when trying to login, and attempting to post entries or comments may result inintermittent errors. For people using certain Internet Service Providers (ISPs), LiveJournal is completely unavailable.
While LiveJournal has experienced some issues with our servers which we have posted about earlier, these issues have been resolved. The current problems are being caused by a sharp increase in malicious traffic which began on December 31. The first wave of that traffic was targeted at profile pages. As a temporary response to this, we disabled profile pages to maintain availability of the rest of the service.
We have already un-blocked profile pages but at this time, but some people using ISPs which have contributed to the malicious traffic are still being blocked by our mitigation system. We understand that there are legitimate users affected by this; in order to allow these people to access the site, we are taking steps to make the list of blocked addresses more precise so no legitimate users are affected.
In case your ISP is being blocked, there are several ways you can try to access the site:
-- The Opera browser has a Turbo mode which works like a proxy server; LiveJournal may be available through this feature in Opera;
-- If have access to an alternate ISP, try connecting through that ISP;
-- You can try using any proxy servers available to you so your request is routed through networks that are not being blocked. If you do this, we strongly suggest you only use the servers you trust; passing your username and password through an untrusted network (e.g. in order to log in) can result in your account being compromised.
We apologize for the inconvenience these problems have caused."