Here is the Riot NOC announcement:
Some of you may have run into server issues, and we apologize for that. We're currently investigating the source of the problem, but our first step is to make sure that our current environment is stable before we work on deploying more long-term fixes. Unfortunately, as part of the process we are performing, we will need to temporarily disable Custom Item Sets.
Once again, we apologize deeply for this inconvenience and we're working hard to get our servers stable – although we are unsure as to how long these repairs may take. We appreciate your patience through all of this!"
( Note: This announcement is currently only posted on the NA service status forums. Unclear if this will also apply to other server or not. Judging by all the )
Additionally, there has been an update on all the recent EUW server problems.
Here is Riot tmx with the update:
"Wanted to give you all a quick update on where we're at. We applied some fixes to our client and successfully tested them on the Public Beta Environment. We decided to deploy it first to the relatively small shard in the Philippines and if everything goes smoothly, we'll roll this out here in EUW and elsewhere. I know this has been a real pain for you guys, but we're close to finally resolving this issue and when we do we'll have a much more comprehensive look at what happened for you and what are our further steps."