I hate to bring such conflicting information into a bug report but I'm at a loss on this!

This only happens for this one repo - I've deleted and re-created it, and setup from scratch with no joy.

HG SCM Poll log insists it's finding changes and is firing a build off of 'Dependent changes detected'.

Started on Mar 19, 2012 11:00:24 PM
[src] $ hg pull --rev default
pulling from /var/hg/repos/mpl
no changes found
[src] $ hg log --style /var/lib/jenkins/jobs/mpl/workspace/tmp2857899180971434423style --branch default --no-merges --prune 9c80c470fa3ef8d89c2352c08babb3f466b9aa24
id:5b02d29a94c43648da2eb0a16f12c2e42eb46c87
files:build.xml:
Dependent changes detected
Done. Took 0.21 sec
Changes found

There's no open/un-merged heads in the repo either:
default 141:9c80c470fa3e

If I downgrade to 1.3.7, it works fine (seems to run a different technique)

HG SCM Poll log from 1.3.7:

Started on Mar 19, 2012 11:11:14 PM
[src] $ hg incoming --style /var/lib/jenkins/jobs/mpl/workspace/tmp1826463261407545325style --no-merges --rev default --newest-first
comparing with /var/hg/repos/mpl
no changes found
Done. Took 53 ms
No changes