Java HotSpot Virtual Machine

All,
Please help!!

I have tested my Application Client Project in WSAD on my pc and it works fine.
I have 1gb RAM on my pc. When I deploy the same app on another xp pc(same as mine but 512mb RAM) I get a heap size error. Here is the exact error:
Incompatible initial and maximum heap sizes specified:

initial size: 268435456 bytes, maximum heap size: 267380736 bytes

The initial heap size must be less than or equal to the maximum heap size.
The default initial and maximum heap sizes are 4194304 and 267380736 bytes.
Usage: java [-options] class [args...]
(to execute a class)
or java -jar [-options] jarfile [args...]
(to execute a jar file)

where options include:
-cp -classpath <directories and zip/jar files separated by ;>
set search path for application classes and resources
-D<name>=<value>
set a system property
-verbose[:class|gc|jni]
enable verbose output
-version print product version
-showversion print product version and continue
-? -help print this help message
-X print help on non-standard options
Could not create the Java virtual machine.
Press any key to continue . . .


Here is the batch file that runs my app:

@echo off
SET appClientEar=C:\corp\apps\mts\jars\MTSClientEAR.ear
set JVM_ARGS=-Xms256M -Xmx256M
set CLIENT_PROPS=C:\corp\apps\mts\jars\medicalclient.properties
set APP_ARGS=
call C:\bnsf\IBM\WebSphere\AppClient\bin\launchClientBNSF.bat "%JVM_ARGS%" %appClientEar% "-CCpropfile=%CLIENT_PROPS%" %APP_ARGS%
@pause


I have changed the value of Xms and Xmx of JVM_ARGS to different size but I sitll get error. Anyone knows what the problem is. Thanks..