Can't verify keys
Just started getting lots of "We contacted the Mollom servers to verify your keys: your keys do not exist or are no longer valid." errors.
I have 3 sites that use Mollom, and I'm only getting this on 2 of them?! How do I go about fixing this? Or are there problems at the Mollom end of things?

I think this error is also
I think this error is also shown when the Mollom servers are not available. This might be due to temporary network errors -- either on your end, or on our end. We didn't notice any downtime on our side. It would be good if you could double check your Drupal's watchdog logs to see if they provide more insight. Let me know what you found in your Drupal watchdog.
It was a Drupal error
I was glad that only 2 or my 3 sites were affected, all on the same web host, as I could do some tests.
I switched the keys over between the site that worked and the site that did not - it was the site that was broken not the keys.
I then noticed that the Http Request Status was flagging up as unavailable in the site status page, and I was getting other strange errors in the dblog (roughly line 760 of common.inc). Reverted to an old database backup, problem went away. Re-enabled the modules I had added since that backup, one by one, problem still not there. And it hasn't come back.
So something had corrupted my Drupal database on two sites such that HTTP Requests weren't working - which probably entirely explains the Mollom downtime I was experiencing. All slighly worrying - such database corruption could happen again, as I am none the wiser - but clearly a Drupal problem not a Mollom problem.
Any chance we could have a Service Status page on this site so that we can see if the Mollom servers are down? And, given you use Client-side Load Balancing, any chance we could be able to see which Mollom servers are being used for which sites - for the same reason? Just a couple of thoughts.
not finding my public key
Just getting same error; also seen:
"warning: strtr() [function.strtr]: The second argument is not an array in ...modules/syslog/syslog.module on line 106. "
via logs, can see report includes:
Error 1000: http://xmlrpc3.mollom.com - Mollom could not find your public key
Tried with one site, inc a database repair/optimize via phpmyadmin - which didn't help w mollom it seems
Another site also giving errors (and this one adding the syslog error: this error just went away, as retried sumbitting the module info)
Not aware of my sites being behind proxy, as I've seen in another thread.
Servers Down
I'm getting the same problems and think it's the Mollom servers. I checked by logs and have this:
Mollom was unavailable (servers: , error: - )
As JamesOakley says it would be good to have a Server Status page as my logs don't show an error I know happened the day before and which again I think is the servers.
HTTP Request fails
Having checked again I think it might be down to this error:
HTTP request status Fails
I'm using drupal 6.4 and applied this patch http://drupal.org/node/245990 but it hasn't worked for me so have disabled Mollom for the time being.
drupal_http_request() ???
just seen another thread on forum, where it mentions drupal_http_request()
and something about needing fsockopen() enabled
I don't know re this for my sites.
- they are working, though; update status works (which does some contacting of external site, and returning info - not sure re mechanism, and if this means anything re mollom)
Fixed
Just found this article that fixes the http request problem: http://collectiveidentity.net/node/13