I'm running Debian Lenny with Icedove 2.0.0.0.16 and the Funambol plugin version 0.5. I'm synching with Horde 3.2.
I first tested the plugin with just contacts (Lightning was not installed). I never experienced a segmentation fault.
Then I installed Lightning (version .8). Every 3rd of 4th time I try to synchronize, I get a segmentation fault. Here's some sample out put:
/usr/lib/icedove/run-mozilla.sh: line 131: 2433 Segmentation fault "$prog" ${1+"$@"}
/usr/lib/icedove/run-mozilla.sh: line 131: 2757 Segmentation fault "$prog" ${1+"$@"}