After Marco's comment, I increased the PermGenSize (-XX:MaxPermSize=128m) in Eclipse and until now the OutOfMemoryError is gone. The flag MaxPermSize is defined as:
"The permanent generation is used to hold reflective of the VM itself such as class objects and method objects. These reflective objects are allocated directly into the permanent generation, and it is sized independently from the other generations. Generally, sizing of this generation can be ignored because the default size is adequate. However, programs that load many classes may need a larger permanent generation."
I didn't needed this setting in Eclipse before. I'm only curious whether this is an Eclipse 3.2 or Java SE 5 issue. I'm also using Netbeans 6.0 on the same JVM, without any problems. The Eclipse 3.2 Callisto needs more space in the permament generation, than the 3.1 version, so it loads more classes.
I had the same problem with BIRT on JBoss and Linux. So the flag -XX:MaxPermSize seems to be important for the future :-).
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