The in portage current stable version of monotone (0.29) is old. There is at least two versions that have been in the tree long enough to be proven stable as there are no bugreports: 0.32 (has been in the tree since 28-dec-2006) and 0.33 (13-mar-2007) and there are currently no open bugs agains them. Please stabilise to a newer version.
Arches please do it, will do x86 today
x86 stable
ppc stable
amd64 ftw