Hi guys,
As Prestachamps mentionned, if you get the "Validation function not found isUrl4Smpl" you should check first the disable overrides option switched (adances parameters > performances). Your shop might still be in a debug mode and you should try with this option set to "no".
Then (if still not working) :
On PS 1.7 you should try to empty cache using the button in advanced parameters > performances.
Then :
You should check if the override/classes/Validate.php file still exists and if it includes the isUrl4Smpl() function.
In any case i would recommand you to contact me using the addons page instyead of posting on the forum. I always reply to addons messages.
Thanks,
Yann