This is essentially the message logged by Anders Viklund:
https://hudson.dev.java.net/servlets/BrowseList?list=dev&by=thread&from=976444

I can not checkout from a label either, I have tried to add it to the field
Depot Path as "//...@LABEL20080218" in the Configure screen.
Regardsless whether the option "Let Hudson Manage Workspace View" is checked or
not the build fails.

What should I do ? Should I comment out the lines in file Workspace.java of
p4java.jar as you suggested ? Or will that break the code ?

Regards,

Ruerd
http://www.numericalexample.com

If the option "Let Hudson Manage Workspace View" is set I get the following
error message:

started
Performing sync with Perforce for: //...@LABEL20080218
Changing P4 Client Root to:
C:\.hudson\jobs\CBS_WSIP_DEV_Rel1b_MessageMonitor\workspace\
Changing P4 Client View to: //...@LABEL20080218 //CBS_WSIP_DEV_Rel1b/...
Caught Exception communicating with perforce. Error in client specification.
Error detected at line 9. Revision chars (@, #) not allowed in
'//...@LABEL20080218'.
For Command: p4 -s client -i
With Data:
===================
Client: CBS_WSIP_DEV_Rel1b
Owner: sw_admin
Description: Created by sw_admin.
Root: C:\.hudson\jobs\CBS_WSIP_DEV_Rel1b_MessageMonitor\workspace\
Options: noallwrite noclobber nocompress unlocked nomodtime normdir
SubmitOptions: submitunchanged
LineEnd: local
View:
//...@LABEL20080218 //CBS_WSIP_DEV_Rel1b/...

===================
FATAL: Unable to communicate with perforce. Error in client specification.
Error detected at line 9. Revision chars (@, #) not allowed in
'//...@LABEL20080218'.
For Command: p4 -s client -i
With Data:
===================
Client: CBS_WSIP_DEV_Rel1b
Owner: sw_admin
Description: Created by sw_admin.
Root: C:\.hudson\jobs\CBS_WSIP_DEV_Rel1b_MessageMonitor\workspace\
Options: noallwrite noclobber nocompress unlocked nomodtime normdir
SubmitOptions: submitunchanged
LineEnd: local
View:
//...@LABEL20080218 //CBS_WSIP_DEV_Rel1b/...

===================

java.io.IOException: Unable to communicate with perforce. Error in client
specification. Error detected at line 9. Revision chars (@, #) not allowed in
'//...@LABEL20080218'.
For Command: p4 -s client -i
With Data:
===================
Client: CBS_WSIP_DEV_Rel1b
Owner: sw_admin
Description: Created by sw_admin.
Root: C:\.hudson\jobs\CBS_WSIP_DEV_Rel1b_MessageMonitor\workspace\
Options: noallwrite noclobber nocompress unlocked nomodtime normdir
SubmitOptions: submitunchanged
LineEnd: local
View:
//...@LABEL20080218 //CBS_WSIP_DEV_Rel1b/...

===================

at hudson.plugins.perforce.PerforceSCM.checkout(PerforceSCM.java:267)
at hudson.model.AbstractProject.checkout(AbstractProject.java:558)
at hudson.model.AbstractBuild$AbstractRunner.checkout(AbstractBuild.java:215)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:181)
at hudson.model.Run.run(Run.java:659)
at hudson.model.Build.run(Build.java:101)
at hudson.model.ResourceController.execute(ResourceController.java:70)
at hudson.model.Executor.run(Executor.java:65)

If the option "Let Hudson Manage Workspace View" is unchecked I get the
following error message:

Performing sync with Perforce for: //...@LABEL20080218
Changing P4 Client Root to:
C:\.hudson\jobs\CBS_WSIP_DEV_Rel1b_MessageMonitor\workspace\
Caught Exception communicating with perforce. the only project path currently
supported when you have multiple workspace views is '//...'. Please revise your
project path or P4 workspace accordingly.FATAL: Unable to communicate with
perforce. the only project path currently supported when you have multiple
workspace views is '//...'. Please revise your project path or P4 workspace
accordingly.
java.io.IOException: Unable to communicate with perforce. the only project path
currently supported when you have multiple workspace views is '//...'. Please
revise your project path or P4 workspace accordingly.
at hudson.plugins.perforce.PerforceSCM.checkout(PerforceSCM.java:267)
at hudson.model.AbstractProject.checkout(AbstractProject.java:558)
at hudson.model.AbstractBuild$AbstractRunner.checkout(AbstractBuild.java:215)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:181)
at hudson.model.Run.run(Run.java:659)
at hudson.model.Build.run(Build.java:101)
at hudson.model.ResourceController.execute(ResourceController.java:70)
at hudson.model.Executor.run(Executor.java:65)