Exception de type OptionalDataException

Bonjour à tous,
J'ai un programme qui marchait correctement et aujourd’hui, il a planté me laissant l'erreur suivante:
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GRAVE: Servlet.service() for servlet surveillance threw exception
java.io.OptionalDataException
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1349)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
        at java.util.TreeMap.buildFromSorted(TreeMap.java:2380)
        at java.util.TreeMap.buildFromSorted(TreeMap.java:2396)
        at java.util.TreeMap.buildFromSorted(TreeMap.java:2396)
        at java.util.TreeMap.buildFromSorted(TreeMap.java:2396)
        at java.util.TreeMap.buildFromSorted(TreeMap.java:2396)
        at java.util.TreeMap.buildFromSorted(TreeMap.java:2396)
        at java.util.TreeMap.buildFromSorted(TreeMap.java:2322)
        at java.util.TreeMap.readObject(TreeMap.java:2268)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.                                                                                                    java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces                                                                                                    sorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974                                                                                                    )
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1849)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1                                                                                                    753)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:19                                                                                                    47)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1                                                                                                    753)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:19                                                                                                    47)
        at java.io.ObjectInputStream.defaultReadObject(ObjectInputStream.java:48                                                                                                    0)
        at net.sf.ehcache.Element.readObject(Element.java:796)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.                                                                                                    java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces                                                                                                    sorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974                                                                                                    )
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1849)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1                                                                                                    753)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
        at net.sf.ehcache.store.compound.factories.DiskStorageFactory.read(DiskS                                                                                                    torageFactory.java:292)
        at net.sf.ehcache.store.compound.factories.DiskPersistentStorageFactory.                                                                                                    retrieve(DiskPersistentStorageFactory.java:202)
        at net.sf.ehcache.store.compound.factories.DiskPersistentStorageFactory.                                                                                                    retrieve(DiskPersistentStorageFactory.java:59)
        at net.sf.ehcache.store.compound.Segment.decode(Segment.java:169)
        at net.sf.ehcache.store.compound.Segment.put(Segment.java:423)
        at net.sf.ehcache.store.compound.CompoundStore.put(CompoundStore.java:13                                                                                                    6)
        at net.sf.ehcache.Cache.putInternal(Cache.java:1290)
        at net.sf.ehcache.Cache.put(Cache.java:1229)
        at net.sf.ehcache.Cache.put(Cache.java:1201)
Quelqu’un aurait une idée de quoi il s'agit?