Playing with OL context and OLON (OpenLayers Object Notation) that is based on JSON I have found that the sample provided on the OLON sandbox in OL repository doesn’t work well with vectors, in fact it ignores vectors at all.  Reading through the code it was quite easy to discover the problem – vector.js (layer) didn’t serialize  “features”, moreover during deserialization, features were nulled. To make OLON properly work in OL 2.7   for vectors, add following to the vector.js (lib\OpenLayers\Layer\Vector.js)

[line 197]
serializable: { 
"args": ["name"], 
"props": ["features"] 
},
[line 238]
if (!this.features) 
this.features = []; 

If you have pure 2.7 OL version installed, following link can help you to make difs against what is needed for OLON to work at 2.7: http://trac.openlayers.org/changeset/7323 …or you may download complete 2.7 version of OpenLayers with OLON extension from the MapBinder sample at http://www.sumbera.com/lab/wmsbinder/getcap.htm since OL there  is not compressed.