Hey all -- I found another cause of linux SimplyConnMgr failures today; this one isn't so much a problem with SimplyConnMgr as it is with the installation instructions and packaging.
The instructions say to install myODBC, and provides a binary package for convenience. It seems, though, that this binary package is broken, or more specifically that it's linked against additional MySQL libraries that are not included in the convenience package.
Today I installed mysql-5 and myodbc-3.51.12 on my AMD64 Gentoo box, and although there's still a little bit of path and permissions related issues with Samba, I was successful in connecting and using the company data from the gentoo box (note, this success still isn't perfect, I'm still having the try-once-and-timeout-but-try-again-and-it-works issue that was reported earlier by someone else).
So, for those of you not installing on the prescribed versions of SUSE and RHEL, try using your system's myODBC packages instead of the one Sage provides -- you might have better luck.