Problem with Debugger & Oracle EXDI in 7.4.1

There appears to be a problem with the debugger in vw 7.4.1.
 
This is what I do:
 
I open a vanilla 7.4.1 image.
I load the Oracle EXDI parcel
I accept the following class method on an arbitrary class (ActionButton class in my example):
 
doInTransaction: aBlock
            | connection |
            connection := OracleConnection new.
            connection username: 'username'.
            connection environment: 'database’.
            connection connect: 'password'.
            connection begin.
            [aBlock ensure: [connection commit]] ensure: [connection disconnect]
 
Then I perform the following piece of Smalltalk code:
 
 
            self halt.
self doInTransaction: [Transcript show: ‘test’]
 
Beause of the halt the debugger opens and I start stepping through the code by using the F6 key (=Step). After pressing it three times, I end up at the end of the block. If I then step one more time I get an exception on OracleNTInterface saying:
 
            unsupported operation
 
I get this error only when I use the debugger to step through the code.
It seems that debugger messes something up if you try to ‘step out of a block’. This doesn’t occur in a VW 7.3.1 image.
Perhaps it has something to do with ExternalInterface subclasses & simulation of byte code execution in the debugger?
 
Has anyone encountered this before? (And is there a fix for it?)
 
Thanks in advance,
Mark
 
The stack trace is here:
 
Unhandled exception: unsupported operation
OracleNTInterface(ExternalInterface)>>externalAccessFailedWith:
OracleNTInterface(OracleInterface)>>OCITransCommit:with:with:
ExternalMethod>>unlinkedCall:arguments:
OracleConnection>>commitExternal
optimized [] in [] in ExternalDatabaseTransaction>>finishTransaction:method:
BlockClosure>>on:do:
optimized [] in ExternalDatabaseTransaction>>finishTransaction:method:
optimized [] in [] in ExternalDatabaseFramework>>participantsDo:
WeakArray(SequenceableCollection)>>do:
optimized [] in ExternalDatabaseFramework>>participantsDo:
BlockClosure>>ensure:
optimized [] in RecursionLock>>critical:
BlockClosure>>ensure:
Semaphore>>critical:
RecursionLock>>critical:
OracleTransaction(ExternalDatabaseFramework)>>participantsDo:
OracleTransaction(ExternalDatabaseTransaction)>>finishTransaction:method:
OracleTransaction(ExternalDatabaseTransaction)>>commit
OracleConnection(ExternalDatabaseConnection)>>commit
optimized [] in [] in ActionButton class>>doInTransaction:
BlockClosure>>valueAsUnwindBlockFrom:
BlockClosure>>ensure:
optimized [] in ActionButton class>>doInTransaction:
BlockClosure>>ensure:
ActionButton class>>doInTransaction:
ActionButton class>>unboundMethod
ActionButton class(Object)>>performMethod:arguments:
ActionButton class(Object)>>performMethod:
TextEditorController(ParagraphEditor)>>evaluateCompiled: