Right, so the library: libgtkhtml-3.1.so.11 doen not exist but one with different numbers does exist?
Have you updated Balsa? (2.2.6 is the latest, I think) Latest versions are more likely to be able to use updated versions of the files they depend on.
Another possibility is just to go get the older version and stick it somewhere balsa can find it.
It may be possible to force balsa to use the updated library... provided the update is backwards compatible.
libtkhtml is optional for Balsa so you cuold just turn off html support
Since developers cannot always garantee backwards compatability in shared libraries, advanced libraries are not always supported. In these situations, either the software goes out of date, or it gets updated to account for or take advantage of xchanges in the newer libraries. It's still annoying but there you are.
Simon