Yes, I had a very similar error on my  Ubuntu machine: 

$uname -a 
Linux sailor 2.6.32-23-generic #37-Ubuntu SMP Fri Jun 11 08:03:28 UTC 
2010 x86_64 GNU/Linux 

I confirm that Mirko's fix worked. For the unwashed, here's what I did 
step by step: 

1. Grabbed latest SRILM (v. 1.5.11) and installed to: 

/home/farrar/Software/LM/srilm 

2. Changed SRILM variable in my Makefile to: 

SRILM = /home/farrar/Software/LM/srilm 

3. I edited my srilm/sbin/machine-type script to look like this 
excerpt: 

else if (`uname -m` == x86_64) then 
    set MACHINE_TYPE = i686-m64 
    #set MACHINE_TYPE = i686 
    else 

4. compiled SRILM as follows: 

$ make MAKE_PIC=yes World 

Step 4 should give no errors. 

5. Grabbed latest Joshua and ran the following: 

farrar@sailor:~/Software/MT/joshua$ ant 
Buildfile: build.xml 

init: 

set-srilm: 

set-java-home: 

srilm: 
     [exec] make: Entering directory `/home/farrar/Software/MT/joshua/ 
src/joshua/decoder/ff/lm/srilm' 
     [exec] g++  -c -fPIC srilm.c -I/usr/local/include/ -I/home/farrar/ 
Software/LM/srilm/include 
     [exec] swig -c++ -java -package joshua.decoder.ff.lm.srilm - 
outdir . srilm_java.i 
     [exec] g++  -c -fPIC srilm_java_wrap.cxx -I/usr/local/include/ -I/ 
home/farrar/Software/LM/srilm/include -I/usr/lib/jvm/java-6- 
sun-1.6.0.20/include/ -I/usr/lib/jvm/java-6-sun-1.6.0.20/include/ 
linux 
     [exec] g++  -fPIC -shared srilm.o srilm_java_wrap.o -loolm - 
ldstruct -lmisc -L/home/farrar/Software/LM/srilm/lib/i686-m64 -o 
libsrilm.so 
     [exec] cp libsrilm.so http://www.cnblogs.com/http://www.cnblogs.com/http://www.cnblogs.com/lib 
     [exec] make: Leaving directory `/home/farrar/Software/MT/joshua/ 
src/joshua/decoder/ff/lm/srilm' 

compile: 
    [javac] Compiling 441 source files to /home/farrar/Software/MT/ 
joshua/bin 
    [javac] Note: Some input files use or override a deprecated API. 
    [javac] Note: Recompile with -Xlint:deprecation for details. 
    [javac] Note: Some input files use unchecked or unsafe operations. 
    [javac] Note: Recompile with -Xlint:unchecked for details. 

BUILD SUCCESSFUL 
Total time: 13 seconds