(Previous LO version had been installed badly ... on USB-stick; and was not used so far.)
Newly announced LO 5.4.1 portable on PortableApps noticed this when update process was started and recommended new full download of LibreOfficePortable_5.4.1_MultilingualStandard.paf.exe.
This was done twice with the same failure when installing.
A second download of the package (identical file) also ended with the same failure, i.e.
aborting the installation with: Could not save the file "Radial05-Sphere-Blue.svg".
Stick-medium should be ok. ...
So the package seems to be corrupt!
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LibreOffice 5.4.1 portable package on Win-7 x64: install fail repeatedly
When you encounter issues like "Could not save" in an NSIS installer it means either (1) the drive is out of space, (2) there is a permissions issue preventing a file/directory from being written, (3) the file is in use by something else and locked by the OS, or (4) there corruption on the drive. If it's not 1 it's usually 4. The release has no corruption issues. If you somehow download only part of the installer or corrupt it locally, it will refuse to run at all with a CRC error. The very first thing the installer does when you run it is check its own integrity.
Sorry for being late (must have expected an e-mail signal for a reaction, or so :-) )
So, thanks for your quick answer - just were looking about that and a new version already was announced... This is just working again.