My recommendation is to move ahead and upgrade from OpenACS 5.5 to OpenACS 5.8.0. OpenACS 5.5.1 is more than 4 years old. Sooner or later, you might want to upgrade, and upgrading the kernel is usually not a big thing. We recently upgraded OpenACS 5.5 to OpenACS HEAD and then to the oacs-5-8 branch, and the upgrade of the core was very smooth (see
https://openacs.org/forums/message-view?message_id=4071801 for the exactly used components). You do not have to upgrade the database (although i would recommend this anyhow).
If for some reason, you can't upgrade to 5.8.0 now, you can check for the differences (diff -r) between your version and the components of the oacs-5-8 branch, and grep for NaviServer. There are probably just a handful of changes.
Concerning bgdelivery: you can probably just upgrade xotcl-core to get this fixed. My first guess would be:
http://cvs.openacs.org/browse/OpenACS/openacs-4/packages/xotcl-core/tcl/bgdelivery-procs.tcl?r1=1.24&r2=1.25&u=3&k=kv
but advancing to newer versions buys you a lot of other advantages (e.g. use of the NaviServer build-in writer threads, which are much better than classical bgdelivery),
Hope, this helps,
-gustaf neumann
