The apt-get command gave me this result:
Reading package lists... Done
Building dependency tree
Reading state information... Done
build-essential is already the newest version.
The following packages were automatically installed and are no longer required:
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 147 not upgraded.
Which seems normal.
I also uninstalled all the linux-restricted-modules packages I could find, as demanded (only those of older kernel version were still on the system).
The installer is still giving the same error. Alack!
Thanks for the help anyway!