Well that's annoying.
After no response from my host I decided to move all the sites to my other server. I shut down this server to stop all the spam email filling the mailqueue. I've now done that so I restarted the server and incredibly I can log into to CWP now. The are 298,722 emails in the mailqueue :-)
If you are using wordpress I suggest you do a search for these files
60dir.php s151.02kb
mail.php 11.36kb
mysql.php 28.11kb
dir24.php 11.19kb
list.php
These are also a valid filenames so view the contents before delete. Most the time they get in the /images of any subdir or the /uploads