I updated one of my WP installations to 3.4.2, the latest and greatest as of this writing. I then went to the Update Plugins page, and clicked the select all checkbox, selected "Update" from the bulk actions, and clicked Apply. After entering my FTP details, I was taken to a screen which told me that plugin update 1/1 had failed because the plugin was already at the newest version.
This was decidedly odd, since I was trying to update 40+ plugins.
I tried selecting all the plugins individually, in case there was some weirdness due to using the Select All checkbox. I got the same error. So I started doing them in batches of 5, on the assumption that there was one plugin with some weird error that was throwing off the system.
I got to the end of the list, and every single plugin had updated successfully.
So I went to one of my other installations, which is at 3.4.1. I tried the Select All button, and all the plugins were updated successfully.
Any suggestions/advice? This seems odd to me, but at least I have a workaround.