Just moved a site to the hosting which support new wordpress . Naturally I decided to upgrade. I know that new WP doesn’t “work” with old theme and the other way around (I’m running ahatualpa on the other site for some time). So I decided to switch to default theme and then upgrade. My admin panel didn’t hit white screen but I end up with site which doesn’t show right sidebars!!! Somehow this default theme change something somewhere. Worth, I deleted theme (from admin panel) and installed it again. And still the same picture!!!
Please, help! I don’t even know where to look.

having the URL would be good - does twenty-eleven work?
try swapping the permalinks to the default and back

1. URL - www.mums-dads.co.uk - sorry, forgot. I was desperately trying different things all the night, was too tired in the end.
2. Twenty eleven doesn’t work, it shows left side bar in the right, right – nowhere could be found. On the other hand, when I switch to Suffusion, I could see right sidebar in a very strange way, of course in Suffusion sidebars are organized differently, so it might be the way it should be...
3. Changing permalinks didn’t help.

Uploaded old Ahatualpa (I still have a copy from time before I moved the site to new hosting) and switch to it. Now everything shows OK.
Now I’ve got extra question. How do I update so i would not have the same problem? I’m still curious why and what happened with my previous attempt to update.

I'm not sure, try this, manually install 377 in it's own folder and call the folder atahualpa377 and try swapping to it again. If that doesn't work, I'd need to take a look (you could send me a PM with an admin ID/pw)

1. Manually install 3.77 – did it sometime ago, doesn’t work. That’s how I installed couple of older ones, both are OK. And I tried upgrading from working older. Still the same picture. Apparently, there was nothing wrong with upgrade the way I was doing it (which was my concern). Problem is with options I used to get the look I wanted. Some of them do not work with newer version. I should say, I’m fare from being an expert, all the changes i did were done by trial. And there was another thing.
2. I have another site, virtually empty with virtually no traffic (none of them are mine, actually just managing). That one was always upgraded on time, now it has “virgin” ahatualpa. I was thinking changing the options one by one, to find the one which cause the problem. It will take some time though, you know, the end of school year + school holidays...
3. Juggledad, thanks for the offer. If I would not be able to figure it out myself, I’ll come back to you.