Second, today everything was humming along and at the end of my work day I checked my account and it sowed last share 7 hours ago. I don't think I had made any contribution during this time. However my GUIMiner was clicking just normal showing 352 MH/S - In statistics, I have no shares from 19195 to 19199 while GUIMiner seem to be running normal. So I'd also like to find out what happened here?
I had this same problem today. One of Slush's servers is having connection problems or something (i'm not sure) but basically whenever I connect to stratum.bitcoin.cz it fails, but someone else posted some slush IP's and the one that currently works is 54.215.3.101
so in GUIminer i set that as my host, stop and restart, and then it started accepting shares and they were being credited to my account (where as before guiminer would generate shares but i received no credit)
Just as a forewarning... I dont think using the direct IP is necessarily a good long term option. From what I understand, Slush uses Amazon AWS. AWS offers load balancing, geolocating\geocaching, and failover based on availability zones. If AWS is like the Azure platform (which I work with for my job), IP addresses are not dedicated. When you set it up, you point your regular public DNS to your AWS FQDN and then the AWS system handles DNS\Routing from there which is what allows the above Amazon services to function with little to no setup. By specifying a server IP address, you are circumventing this feature. This may temporarily resolve an issue such as today when a specific load balancing server is down or a specific geolocation\availability zone is malfunctioning in a way that AWS doesn't recognize the malfunction and remove the specific server from the rotation. However, long term you don't get the benefits of those options, which would be crucial if the specific server you chose fails. Also, without dedicated IP's, there is no guarantee that server will continue to be located there after an IP lease renewal or a server reboot.
I could be totally wrong about this, but this is why I wont use direct IPs. I experienced the issues earlier today and I resolved them by bouncing NIC's on all my machines to reset my connection and flush old\invalid DNS data. I also bounced the proxy software on 2 of my machines that use that. I never stopped CGMINER or GUIMINER (on my windows machine... I know I know but CGMINER throws fits on that machine) and the network bounce took less than a minute.
Just my $0.02