There are problems with the signal to noise ratio in CM18 & CM19 due to the poor quality of the network. AFAIK these are posted on the server status page, but not sure what is happening with regard to resolving the issues at the moment.
I am sure Ignition has more information... infact i'm sure i've seen an explanation on this forum before....
EDIT: lots of topics regarding the same subject here:
http://www.cableforum.co.uk/board/se...earchid=405999