This is a Windows-only issue, due to OOo not supporting long pathnames there,
see issue 50885.  What is unfortunate here is that, due to the mechanisms used
to keep OOo installations relocatable, during OXT installation the problematic
xcs/xcu files within the extension are accessed with slightly shorter pathnames
than during subsequent OOo starts (where the paths contain
"com.sun.star.comp.deployment.configuration.PackageRegistryBackend/.." segment
sequences, making them rather long).  Therefore, OXT installation works fine,
while subsequent OOo starts run into an error.

Issue 50885 is targeting OOo 3.3 as well, so I make this issue a duplicate of
that issue.

*** This issue has been marked as a duplicate of 50885 ***

not acceptable. The SRB extension works in the master and didn't work in the
cws. Maybe the fix depends on other things , but then we need to fix these
things inside this CWS.

reassign back to sb

@msc:  That the extension can be installed and works fine for you on MWS is by
chance.  Chose a somewhat longer pathname for the OOo user installation (e.g.,
have a longer user name if the OOo user installation is at its default location
underneath $SYSUSERCONFIG), and it will start to break down on MWS as well.

I identify two potential differences between MWS and sb111:

1  The long pathname problem apparently starts to already appear for somewhat
shorter paths (of xcs/xcu files within extensions) on sb111 than on MWS. 
However, as the long pathname problem in general appears on both, MWS and sb111,
just differently for slightly different inputs, I do not see the need to address
that problem on sb111, given that issue 50885 will be fixed for OOo 3.3.

2  On sb111 there apparently are situations (depending on user installation
location and paths of xcs/xcu files within extensions) where installing an
extension works but subsequent OOo starts fail, as I explained above (as the
pathnames used during extension installation can be slightly shorter than those
used during OOo start up).  I do not know whether or not something similar can
happen on MWS (i.e., whether there are also situations there where extension
installation succeeds while some later operation fails).  However, making sure
that, with issue 50885 unfixed, sb111 would never encounter this unfortunate
combination, would require rather large code modifications.  Given that issue
50885 will be fixed for OOo 3.3, those code modifications would be both a waste
of resources and a lasting increase in source complexity that would become
unsubstantiated as soon as issue 50885 is fixed.

I expect mav's fix for issue 50885 to be available within a week or so, and will
merge that fix into CWS sb111 as soon as it is available.

merged CWS fwk137 (fixing issue 50885) into CWS sb111

@msc: please verify

The office starts now after installing the extension. -> set issue to verified

But the extension does not work. This is the new issue 108905.