ConcurrentModificationException using spymemcached with spring integration

hi, I use mecached and java spymemcached client version2.8.1
when i use the spymemcached integerated with Spring
I get:
java.util.ConcurrentModificationException
in the AbstractLog:
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
at java.util.HashMap$KeyIterator.next(HashMap.java:828)
at net.spy.memcached.util.StringUtils.join(StringUtils.java:41)
at net.spy.memcached.protocol.ascii.BaseGetOpImpl.toString(BaseGetOpImpl.java:227)
at java.lang.String.valueOf(String.java:2826)
at java.lang.StringBuilder.append(StringBuilder.java:115)
at net.spy.memcached.protocol.TCPMemcachedNodeImpl.toString(TCPMemcachedNodeImpl.java:469)
at java.util.Formatter$FormatSpecifier.printString(Formatter.java:2794)
at java.util.Formatter$FormatSpecifier.print(Formatter.java:2677)
at java.util.Formatter.format(Formatter.java:2433)
at java.util.Formatter.format(Formatter.java:2367)
at java.lang.String.format(String.java:2769)
at net.spy.memcached.compat.log.AbstractLogger.debug(AbstractLogger.java:98)

I checked this using spymemcached without spring integration and it worked fine.
I used the same code the spring wrapper for MemcachedClient uses and it worked.
Any ideas why this happens, are there any known issues with this integration?
thanks