I just did a quick search through startlogics support pages and found this
read_article.bml?kbid=7137;keywords=mysql
so your mysql host should be
AcctUsername.startlogicmysql.com
You mentioned you are using webaddess.startlogicmysql.com.. Are they the same?
If that is not it, then the next step would be to contact your host and find why the connection is failing.
Thanks
Tom