jul-to-slf4j-1.5.10.jar
MANIFEST.MF is missing OSGI Informations

...
Import-Package: org.slf4j;version="1.5.10",
org.slf4j.spi;version="1.5.10"
Export-Package: org.slf4j.bridge;version="1.5.10"
...

so you have to wrap it by yourself or as workaround use the Bundle provided by
SpringSource:

http://www.springsource.com/repository/app/bundle/version/detail?name=com.springsource.slf4j.bridge&version=1.5.10

thx
ekke