Every time I publish my site to the web, I get an error telling me to "click cancel and then use the assets panel to fix asset problems, or click OK to continue". When I check the asset panel, there are no errors, no red question marks, no yellow triangles or sizing error indicators. So I go ahead and upload and it's fine. But the false reading is annoying -- and of course, after awhile I'm tempted to ignore it and click past, which could be a problem if there really we're errors in the asset panel.
We have heard of this from other users as well, and I understand how this can be annoying. I suggest logging a bug with the product team using this link.