Strange interaction between R package XLConnect and choose.files()

[admin]

I observe the following strange behaviour:

Using the R-console (2.15.2, Windows 7, 32 bit), I get:

> choose.files() # works fine here
character(0)
> library(XLConnect)
Lade nötiges Paket: XLConnectJars
Lade nötiges Paket: rJava
Error : .onLoad in loadNamespace() für 'XLConnectJars' fehlgeschlagen, Details:
  Aufruf: .jinit()
  Fehler: Cannot create Java virtual machine (-4)
Zusätzlich: Warnmeldung:
Paket ‘rJava’ wurde unter R Version 2.15.3 erstellt 
Fehler: Paket ‘XLConnectJars’ konnte nicht geladen werden

The choose.files() call works fine (I just clicked "Cancel"), but obviously XLConnect could not be loaded due to some JVM related problem.

Now, restarting the R-console and issuing the same two commands in different order:

> library(XLConnect)
Lade nötiges Paket: XLConnectJars
Lade nötiges Paket: rJava
XLConnect 0.2-4 by Mirai Solutions GmbH
http://www.mirai-solutions.com ,
http://miraisolutions.wordpress.com
Warnmeldung:
Paket ‘rJava’ wurde unter R Version 2.15.3 erstellt 
> choose.files() # returns after a few seconds without ever displaying a file choser
character(0)

So the XLConnect package loads fine, but the choose.files() call never displays a file chooser and returns "character(0)" after some seconds.
When I run the same code in R-Studio, everything works fine in both ways.

I already tried to increase the Java heap space (as I found this hint in some other threads/forums) but it did not help.

Any explanations or tips how to solve that problem?