I wanna change the joomla error reporting to maximum, so we can now the detail error on that blank page

Btw I just installed JomSocial Professional 4.1 on a fresh test site, built with Joomla 2.5, and it all works fine, so that can't be the reason.

our project manager said, this is can be caused by the 3rd party, so you need check your extension one by one, if you can active and show the php error, it can be easily to fix it

That is your way to deal with the mess I got into, to blame it on other extensions, and think your work is done? My site is a half working mess because I tried to upgrade to your latest software, which is advertised to work fine. I had expected better support than that.

this is 3rd party issue, we cant do nothing... but if you show the detail error I can give you the solution.. I cant fix it if I dont know where its coming from..

I am getting really angry now! This is bad support. It's NOT a 3rd party issue. I set up a test website without 3rd party extension, and
went through the same upgrade process, starting at JomSocial 2.6.3 - same mess! I even gave you access to that test site, but you didn't even care to look at it. Like I said, I suspected the cause to be that, when running the community installer multiple times in a row (which I have to, when upgrading from 2.6.3). the installer steps are being cached by the browser, so it looks like it's working, but it isn't.

Sure enough, after installing the browser plugin 'Cache Killer', and trying it all again, the upgrade process works. So I solved it myself in the end, while you are still blaming 3rd party extensions.

Really unsatisfying support.

I am sorry for this, my last request is need your help to activate the debugging error reporting, so we will know why the detail issue, since you are using different configuration method so we hard to inspect by ourself, so we dont know this issue caused by 3rd party or from our Jomsocial, since we also use Jomsocial 4.1 and Joomla 2.5 on this site (jomsocial.com) and works perfectly

but at the end I glad you fixed this issue..

have a nice day!

So I partly did the iJoomla installer upgrade path, with the Chrome extension 'cache killer' activated. This helped, but the method update_17() crashed half way, without an error message. So I wrote a script to execute the rest of update_17(). which worked. Then manually upgraded to 4.0.10 , just to test. went fine. Then tried the iJoomla installer again to upgrade to 4.1. Went fine, except that the method update_18() wasn't executed at all, so I had to manually created those 4 ..._stats tables. Looks like it went fine, but the upgrade is a real mess, I must say.

Not sure if my problem was finally fixed (by myself), so I'm keeping my fingers crossed.

I see, thank you for sharing ;).. seems you already fixed by yourself..