Hi,
This error is in the startup.log
!SESSION 2012-05-28 08:08:10.322 -----------------------------------------------
eclipse.buildId=unknown
java.fullversion=JRE 1.6.0 IBM J9 2.4 Windows Server 2003 x86-32 jvmwi3260sr9-20110712_86792 (JIT enabled, AOT enabled)
J9VM - 20110712_086792
JIT  - r9_20101028_17488ifx19
GC   - 20101027_AA
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=en_GB
Framework arguments:  -noSplash true true true
Command-line arguments:  -console -data c:/lotus/domino/data/amlnotesdev01/domino/workspace -noSplash true -clean true -noExit true
!ENTRY org.eclipse.osgi 4 0 2012-05-28 08:08:10.322
!MESSAGE Bundle com.ibm.domino.osgi.core@15 not found.
!ENTRY org.eclipse.update.configurator 4 0 2012-05-28 08:08:12.478
!MESSAGE C:\lotus\domino\data\amlnotesdev01\domino\workspace\.config\domino\eclipse\plugins\plugins is not a valid plugins directory.

These errors are repeated sveral times in error-log-0.xml
CLFAD0331W: NSF Based plugin contribution denied because signer does not have required access: :UpdateSite.nsf
CLFAD0334W: Feature com.ibm.xsp.extlib.feature_8.5.3.20120320-1003 skipped

The plugins were installed on the client and server under my id, which has manager access to updatesite.nsf and is listed in 'Sign or run unrestricted methods and operations' config setting on the server.  This line has been added to the notes.ini 'OSGI_HTTP_DYNAMIC_BUNDLES=UpdateSite.nsf'

Double checked what I did and pretty certain I followed the install instructions to the letter.  Screenshot below taken from updatesite.nsf

Thanks