I just upgraded to EE2.3.1 on a Wamp server (PHP 5.2.8 and MySql 5.1.3) to test my site before upgrading the server. I ran the Server Compatibility Wizard and it says all is well. My image resizing protocol is set to GD2.
I get the above error in both File Sync and in File Upload. The directory cannot be write protected, because the _thumb subdirectory is being created, and in the case of File Sync at most 2 files get synced, but I get the error on all the other files (.jpg, .gif, and .png) in the directory.
I saw in a previous thread that it was recommended that GD2 be reloaded. If that is the case, I will need instructions on how to do that! thanks!