Lightroom 3.5RC says "Can't update this collection: An internal error has occurred: assertion failed!" when I try to Publish a Hard Drive service that has modified photos. I use it regularly and have had no problems prior to 3.5RC.
A couple more observations:
- Of the dozen or so images needing updated, the first ends up in a "tmp" folder within the export location before the process errors out.
- To test for a security issue, I gave the "Everyone" user full control in my export folder. It didn't help. Along the same lines, I also temporarily removed the existing versions of the modified files to export. Again, didn't help.
This seems to exist for smart collections that were created prior to upgrading to 3.5. The work-around seems to be to export the collection settings then import them again.
I've been able to repro this, and have logged a bug. The problem exists with publish collections that were created in LR 3.3 or earlier. The only workarounds I've found for you to use in the interim is to either recreate the collection in LR 3.5 or (as Darren suggests in the case of a smart published folder), export the collection settings and re-import.