Steps to reproduce :
1.Install build-flow and envinject
2.Create a build-flow job
3.Successfully run the build-flow job
4.Restart jenkins

The following occurs:
No builds will be displayed in the history. Relevant jenkins log entry is attached.

08.08.2012 12:33:25 hudson.model.RunMap load
WARNING: could not load E:\Jenkins\jobs\test111\builds\2012-07-31_17-20-02
hudson.util.IOException2: Unable to read E:\Jenkins\jobs\test111\builds\2012-07-31_17-20-02\build.xml
at hudson.XmlFile.unmarshal(XmlFile.java:164)
at hudson.model.Run.reload(Run.java:290)
at hudson.model.Run.<init>(Run.java:279)
....
Caused by: com.thoughtworks.xstream.converters.ConversionException: Could not call org.jenkinsci.plugins.envinject.EnvInjectPluginAction.readResolve() : null : Could not call org.jenkinsci.plugins.envinject.EnvInjectPluginAction.readResolve() : null
---- Debugging information ----
message : Could not call org.jenkinsci.plugins.envinject.EnvInjectPluginAction.readResolve() : null
cause-exception : com.thoughtworks.xstream.converters.reflection.ObjectAccessException
cause-message : Could not call org.jenkinsci.plugins.envinject.EnvInjectPluginAction.readResolve() : null
class : com.cloudbees.plugins.flow.FlowRun
required-type : org.jenkinsci.plugins.envinject.EnvInjectPluginAction
path : /com.cloudbees.plugins.flow.FlowRun/builds/edgeMap/entry/org.jgrapht.graph.IntrusiveEdge/target/actions/org.jenkinsci.plugins.envinject.EnvInjectPluginAction
line number : 59
-------------------------------

Note:
Manually deleting all lines containing "envinject" from Jenkins\jobs\test111\builds\2012-07-31_17-20-02\build.xml allows for the build to properly be loaded and displayed in the build history.