test results are not cleared in the test tree

Open WD with test results, right mouse click on some result and select "clear results". There is no visual effect. Result remains unchanged(uncleared). However, working directory is cleared if look into WD on the disk.
also, there is a log in workdir:

...
[15jan2007 17:40MSK] Bad result file detected, attempting to recover CLDC_(JSR_30_and_JSR_139)/com/sun/cldc/cldc1_0/functional/cpack/c04_3_1/c0431406/test0431406#testcase1.
[15jan2007 17:40MSK] Starting test run
[15jan2007 17:41MSK] Completed test run: ok
[15jan2007 18:05MSK] Error reading test result cache (java.io.UTFDataFormatException: malformed input around byte 110)
java.io.UTFDataFormatException: malformed input around byte 110
  at java.io.DataInputStream.readUTF(Unknown Source)
  at java.io.RandomAccessFile.readUTF(Unknown Source)
  at com.sun.javatest.TestResultCache.readCacheEntries(TestResultCache.java:546)
  at com.sun.javatest.TestResultCache.readCache(TestResultCache.java:515)
  at com.sun.javatest.TestResultCache.doWork(TestResultCache.java:294)
  at com.sun.javatest.TestResultCache.doWorkUntilDone(TestResultCache.java:211)
  at com.sun.javatest.TestResultCache.access$000(TestResultCache.java:28)
  at com.sun.javatest.TestResultCache$1.run(TestResultCache.java:119)

This problem is hard to reproduce, but sometimes it rises and it's confusing.
Seems like some cached results problem.