To debug SQL Backup, put the -sqbdebug
flag on the SQL Backup Agent.
This is not debugging so much as an activity log that shows what was happening, and I'm not too confident it will tell you what the IPC problem is.
It may also be useful to use the SQL Backup installation checker and send us the output:
ftp://support.red-gate.com/utilities/Ch ... nstall.zip
then use cscript CheckSQBInstall.vbs
If all else fails, we can see about upgrading to v6 which has an IPC mechanism that is more stable.