Thank you, Levente, for this valuable hint :-)
This paved the road to sucess!
The following process now has worked for me (adapted from Eliot's instructions)
1) Download http://files.squeak.org/6.0alpha/Squeak6.0alpha-17086-32bit/
2) Verify the last update map loaded by opening a Workspace. Then evaluate MCMcmUpdater default lastUpdateMap This gives me 'http://source.squeak.org/trunk%27-%3E402
3) Open a Monticello Browser and and click on 'http://source.squeak.org/trunk'; click 'Open'
4) Locate the second to last entry called 'update' and there 'update-eem.403.mcm' (see attachment); click on 'Load'
5) Load (or merge) update-eem.406.mcm.
6) Save your image.
7) Locate the Kernel package and click on 'Kernel-eem.1078'; "Load"
8) Save your image.
9) Choose 'Update' from the Squeak menu.
RESULT ------------
As of today this got me to version #17138
--Hannes