[WP8.1] Cannot install app anymore!

[BHolst]

Info:
Model: SAMSUNG GT-I8750
OS version: 8.10.14157.200 (no updates available!)

Problem:
First I couldn't upgrade to the latest(?) version of Spotify. It downloaded OK but 30%-40% into the installation it stops and say "Attention required, Tap here". I "Tap here" and get a generic "We're having trouble installing this app..." error message and I can Try Again or Cancel (none of them end up installing the app).

Did all the tricks I could think of (reboot, check for updates to OS, move app from SD card to Phone, tried on both Wi-Fi and 3G) but nothing worked. Finally I decided to uninstall Spotify to see if the existing version was the problem. Apparently not, because now I can't install again, get the same error message! 😞

Don't hesitate to ask for more info, but please help!

Thank you in advance!

//Brian