Hello,
I had some problems installing the eclipse plugin as well. But I think I found a solution.
After selecting the update site for the designer I see the following tree:
Activiti BPMN Designer
– Activiti Eclipse BPMN 2.0 Designer
When I disable the checkbox "Group items by category", the following flat structure appears:
Activiti Eclipse BPMN 2.0 Designer 0.5.1
EMF - Eclipse Modeling Framework Core Runtime 2.6.0.v20100614-1136
EMF - Eclipse Modeling Framework Runtime and Tools 2.6.0.v20100614-1136
EMF Code Generation 2.6.0.v20100614-1136
EMF Code Generation UI 2.6.0.v20100614-1136
EMF Common 2.6.0.v20100614-1136
EMF Common UI 2.6.0.v20100614-1136
EMF Data Binding 1.2.0.v20100614-1136
EMF Ecore Code Generator 2.6.0.v20100614-1136
EMF Ecore Code Generator UI 2.6.0.v20100614-1136
EMF Ecore Edit 2.6.0.v20100614-1136
EMF Ecore Mapping 2.6.0.v20100614-1136
EMF Ecore Mapping Editor 2.6.0.v20100614-1136
EMF Edit 2.6.0.v20100614-1136
EMF Edit Data Binding 1.2.0.v20100614-1136
EMF Edit UI 2.6.0.v20100614-1136
EMF Mapping 2.6.0.v20100614-1136
EMF Mapping UI 2.6.0.v20100614-1136
EMF Model Converter 2.6.0.v20100614-1136
EMF Model Transaction 1.4.0.v20100428-2315-377-8s734C3E7D15D6B
EMF Model Transaction Workbench Integration 1.4.0.v20100428-2315-36-8s734C367E3CBC7
EMF Sample Ecore Editor 2.6.0.v20100614-1136
EMF Validation Framework 1.4.0.v20100428-2315-479-9oB56N5BBR6LCA6
Graphical Editing Framework Draw2d 3.6.0.v20100519-2050-45-7w3121163602336
Graphical Editing Framework GEF 3.6.0.v20100519-2050-777B-81A2Bz-69793A8B83447
Graphiti (Incubation) 0.7.0.v20101005-1338
After selecting all entries and installing them, the plugin worked.
Tobias