I had the same problem with my modern theme after upgrading to 22.214.171.124.
I took a look at the files for a new installation of 126.96.36.199 and noticed that all the files that used to be in the “default” folder are now in the “base” folder. But on my upgraded installation, I still had all the files in the default folder. I resolved it by replacing the “default” and “base” folders in the APP section by using the files from the download of a fresh 188.8.131.52. I did the same for the SKIN section. Try that.
No - that didnt help me, because my files were already correct. The way I upgrade is I took my existing install of 1.3 and copied the fresh install files of 1.4 over the 1.3 files. So all the files are in the right place or were overridden by the right ones.
The CSS is stil like that i,e, the web page is not centered.
I had this same problem. It turns out that my custom theme was built on the 1.3 default theme. It seems that in 1.4 they scrapped the old default theme and recoded it in a different way. So when my custom theme when and tried to fall back on the default theme files it was using files that are different and they didn’t play nice.
To fix this temporarily, I renamed the /app/design/frontend/base folder to /app/design/frontend/base.bak to get it out of the way. I then renamed /app/design/frontend/default/default to /app/design/frontend/default/default.bak to get that out of the way. I then put the 1.3 default theme back in /app/design/frontend/default/default so that my custom themes would fall back on the files that it knows and loves. This seems to be working for now, though it will probably be wise to recode any custom themes to jive with the new theme files.
As for the modern theme, I’m just assuming that they haven’t released a version that jives with the new theme files yet, so its probably looking for the old 1.3 default theme to build off of itself.