3
This has fixed problems for many users:
Well the good news is that there is a fix for this.
Now - please note: this hasn't been fully tested as of yet, but it should sort out the problem.
I would recommend you fully backup database & site of course before usage....
Anyway - download
this file - and replace the current version of /class/xoopsform/form.php with this. You will need to right click 'save as' and select all files as the file choice in order to save it as a .php file ready to upload.