New error causing lockup in Fedora 8

I have recently moved my system from Fedora 7 to Fedora 8.  I now have
it up and running well, with OpenAl and GL installed.  But when I
attempt to run Cobalt and open one of the lessons that Americo wrote,
upon selecting the place button the window brings up two error message
windows, both covered by the Cobalt window, and seems to freeze.

Since this worked in F7, the error is most likely system related. But
since I get no notices from the system, I need to know where to look to
find the exact problem.  So if one of you can point me to the location
or the system call, then I can do some more research to find the error.
It is definitely related to the mouse move I can see that, but I cannot
tell what it doesn't like.

The SqueakDebug.log contains the following:

MessageNotUnderstood: UndefinedObject>>isCurrent
6 May 2008 10:41:18 am

VM: unix - a SmalltalkImage
Image: Croquet1.0beta [latest update: #2]

SecurityManager state:
Restricted: false
FileAccess: true
SocketAccess: true
Working Dir /home/lesh/Software/Cobalt/cobalt-base-current-build
Trusted Dir /home/lesh/Software/Cobalt/cobalt-base-current-build/secure
Untrusted Dir /home/lesh/Software/Cobalt/cobalt-base-current-build/My
Squeak

UndefinedObject(Object)>>doesNotUnderstand:
        Receiver: nil
        Arguments and temporary variables:
                aMessage: isCurrent
        Receiver's instance variables:
nil

CobaltMaster(CroquetParticipantWithMenu)>>mouseEnter:
        Receiver: a CobaltMaster<Cobalt>(3457)
        Arguments and temporary variables:
                evt: [640@89 528@13 mouseEnter 25644]
        Receiver's instance variables:
                bounds: 111@77 corner: 711@477
                owner: a PasteUpMorph<world>(1347) [world]
                submorphs: #()
                fullBounds: 111@77 corner: 711@477
                color: (Color r: 0.69 g: 0.721 b: 0.772)
                extension: a MorphExtension (2688) [externalName = Cobalt ]  [other:
(clipSubm...etc...
                harness: a CroquetHarnessWithMenu
                lastBounds: 111@77 corner: 711@477
                dock: a TZoomNavigatorMorph(888)
                windowData: nil

CobaltMaster(Morph)>>handleMouseEnter:
        Receiver: a CobaltMaster<Cobalt>(3457)
        Arguments and temporary variables:
                anEvent: [640@89 528@13 mouseEnter 25644]
        Receiver's instance variables:
                bounds: 111@77 corner: 711@477
                owner: a PasteUpMorph<world>(1347) [world]
                submorphs: #()
                fullBounds: 111@77 corner: 711@477
                color: (Color r: 0.69 g: 0.721 b: 0.772)
                extension: a MorphExtension (2688) [externalName = Cobalt ]  [other:
(clipSubm...etc...
                harness: a CroquetHarnessWithMenu
                lastBounds: 111@77 corner: 711@477
                dock: a TZoomNavigatorMorph(888)
                windowData: nil

MouseMoveEvent(MouseEvent)>>sentTo:
        Receiver: [640@89 528@13 mouseEnter 25644]
        Arguments and temporary variables:
                anObject: a CobaltMaster<Cobalt>(3457)
        Receiver's instance variables:
                timeStamp: 25644
                source: a HandMorph(3634)
                type: #mouseEnter
                buttons: 0
                position: 528@13
                handler: nil
                wasHandled: true
                startPoint: 640@89
                trail: #(639@90)


--- The full stack ---
UndefinedObject(Object)>>doesNotUnderstand:
CobaltMaster(CroquetParticipantWithMenu)>>mouseEnter:
CobaltMaster(Morph)>>handleMouseEnter:
MouseMoveEvent(MouseEvent)>>sentTo:
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
MouseMoveEvent>>sentTo:
CobaltMaster(Morph)>>handleEvent:
CobaltMaster(CroquetParticipantWithMenu)>>handleEvent:
[] in MouseOverHandler>>processMouseOver: {[:m | (m == focus    or: [m
hasOwner: focus])   ifTrue: [localEvt := evt    ...]}

Hi Les,