@Dji Took your advise, but it didn't help
I discovered the DEP thing wasn't crucial to the problem, it was an after-process Windows did (DEP = Data Execution Prevention) and even with altered settings and rebooting it didn't help to get LibreOffice working through Liberkey.
Soo... I tried if the PortableApps version via the PortableApps Suite would work and then I got a nice warning which actually got me some clue: it said it couldn't perform the action (opening LibreOffice through PAsuite) because there was a space (or 2) in the filepath.
I did some experimenting and got rid of the spaces in a folder (-name) in the root of my Liberkey suite (on my hardrive), and it worked for the LO (LibreOffice) in the PA suite, but still not for the LO in Liberkey. So now I'm clueless again why it won't work via Liberkey.
I can click on LO in LK suite, I get a splashscreen with a statusbar, and when it's half way, it stops working and closes.
Could it possibly have something to do with Java? At PA it was recommendd to install portable Java in the suite (in "common files"), how is this managed by Liberkey?
@opendevLiberKey 5.1 - 20110201115312 - en (1.01)
Root folder: C:\Users\...\Documents\A_USB_8GB\Liberkey\
7-Zip - 9.20 - Installer\7z.exe
LiberKey Inst - 1.2.0.111 - Installer\LkInst.exe
KEY Files Assoc' - 1.8.0.31 - KeyFileAssoc\KeyFileAssoc.exe
LiberKey Menu - 5.1.0.18 - LiberKeyMenu\LiberKeyMenu.exe
LiberKey Portabilizer - 2.0.0.377 - LiberKeyPortabilizer\LiberKeyPortabilizer.exe
LiberKey Apps Closer - 1.0.0.32 - LKAppsClose\LKAppsClose.exe
Liberkey Apps Version Checker - 1.3.0.181 - LKAppsVCheck\lkAppsVCheck.exe
LiberKey Disk Ejector - 0.1.15 - LkDiskEjector\LkDiskEjector.exe
LiberKey USB Eject - 2.0.0.11 - LkDiskEjector\LkEject.exe
LiberKey Portable Desktop Shortcuts - 0.1.0.55 - PDS\PDS.exe
WAK - 1.0.13 - WAK.exe
[edit: removed name]