On my side iMacros 8.8.2 + FF31 works perfectly !No, not to FF31 but FF30, as FF31 broke iMacros for FF v8.8.2... (for .js Scripts)
The only issue with 8.8.2 addon is the incompatibility with the new HTTP cache which was activated in FF32 (Maybe Palemoon developers had activated it one version earlier as it was already present in FF30 but not activated)
I keep FF31 on all my platforms, but I use FF33 (and FF32 before) for development and issue tracking and I don't have any issue to now.
You just have to set the property browser.cache.use_new_backend_temp to false in your "about:config" for using the old cache instead of the new one.
Addons 8.8.4 or 8.8.5 are completely unstable on any version of Firefox from 31 to 33, freezing on some TAG (link, select ...) or giving errors despite the TAG was found... (But the CLEAR command works no matter what version of the cache is activated).