If you got a ClassCastException on the ConfigurationAdmin class during a start of a bundle which uses declarative services then it might be that the start order of the bundles is not correct.
Exception:
org.apache.felix.cm.impl.ConfigurationAdminImpl cannot be cast to org.osgi.service.cm.ConfigurationAdmin
The following bundle levels provide a working configuration on my system:
g! lb apache START LEVEL 10 ID|State |Level|Name 0|Active | 0|System Bundle (3.0.8) 20|Active | 2|Apache Felix Remote Shell (1.1.2) 23|Active | 3|Apache Felix File Install (3.1.10) 34|Active | 2|Apache Felix Gogo Runtime (0.8.0) 177|Resolved | 1|Apache Felix Shell Service (1.4.1) 205|Active | 2|Apache Felix Gogo Command (0.8.0) 242|Active | 2|Apache Felix Configuration Admin Service (1.2.4) 269|Installed | 1|Apache Felix Shell TUI (1.4.1) 294|Active | 2|Apache Felix Gogo Shell (0.8.0) 309|Active | 2|Apache Felix EventAdmin (1.2.8) 315|Active | 2|Apache Felix Declarative Services (1.6.0) 318|Active | 4|Apache Commons Logging (1.1.1) 319|Active | 4|Apache Commons IO (1.4.0) 322|Active | 4|Apache Commons Lang (2.5.0) 325|Active | 4|Apache Commons Collections (3.2.1) 327|Active | 4|HttpComponents Client (4.2.1) 331|Active | 4|Apache Commons Codec (1.6.0) 332|Active | 4|HttpComponents Core (4.2.1) 336|Active | 4|Apache Log4J (1.2.16) 337|Active | 2|Apache Felix Bundle Repository (1.6.6) 339|Active | 2|Apache Felix Log Service (1.0.0) 340|Active | 2|Apache Felix iPOJO (1.8.0) 341|Active | 2|Apache Felix iPOJO WebConsole Plugins (1.6.0) 342|Resolved | 2|HTTP Service (1.0.0) 343|Active | 2|Apache Felix Web Management Console (3.1.2) 344|Active | 2|Apache Felix Metatype Service (1.0.2)