poi nosuchmethoderror

getting the following and not sure why. the path looks correct and the jar file has the class workbook with a method getsheetat.

Message . . . . :   Java exception received when calling Java method.
Cause . . . . . :   RPG procedure CRPGPROC in program DONNA/PRCFILES received
  Java exception "java.lang.NoSuchMethodError:
org/apache/poi/ss/usermodel/Workbook.getSheetAt(I)Lorg/apache/poi/ss/us"
  when calling method "getSheetAt" with signature
  "(I)Lorg.apache.poi.ss.usermodel.SHEET;" in class
  "org.apache.poi.ss.usermodel.Workbook".


os: 7.1
java version "1.6.0"
Java(TM) SE Runtime Environment (build pap6460_26sr5ifix-20130304_01(SR5+IV37419))
IBM J9 VM (build 2.6, JRE 1.6.0 OS/400 ppc64-64 Compressed References jvmap6460_26sr5-20130207_01_cr (JIT enabled, AOT enabled)
J9VM - R26_Java626_SR5_20130204_0851_B137148
JIT  - r11.b03_20130131_32403
GC   - R26_Java626_SR5_20130204_0851_B137148_CMPRSS
J9CL - 20130204_137148)
JCL  - 20130303_02

classpath:

/home/donna/poi/poi.jar:
/home/donna/poi/poi-ooxml.jar:
/home/donna/poi/dom4j.jar:
/home/donna/poi/xbean.jar:
/home/donna/poi/jsr.jar:
/home/donna/poi/poi-ooxml-schemas.jar:
/home/donna/poi/poi-scratchpad.jar

jar files:
/home/donna/poi/dom4j.jar
/home/donna/poi/jsr.jar
/home/donna/poi/poi.jar
/home/donna/poi/poi-ooxml-schemas.jar
/home/donna/poi/poi-scratchpad.jar
/home/donna/poi/xbean.jar

code:
d SSWORKBOOK_GETSHEETAT...
d                 pr                  LIKE(SSSheet)
d                                     EXTPROC(*JAVA:WORKBOOK_CLASS
d                                     :'getSheetAt')
d SHEETIDX                            LIKE(JINT) VALUE

d WORKBOOK_CLASS  c 'org.apache.poi.ss.usermodel.-
d Workbook'

SSWorkbook=ss_open(%trim(filename));                  --- works fine. pointer not null.
SSSheet = SsWorkbook_getSheetAt(SSWorkbook : 0  );   --- bombs