Post Command problem when using VBScript

Hi ,
I am running TI Home 2009 (build 9809) on an XP Pro machine (SP3 installed and fully updated with Microsoft updates. I have a VBScript command file which renames the .tib file created by the backup process, prefixing the file name with the date in the format "YYYYMMDD_", thus allowing me to keep an unlimited number (well, enough!) of backups on a 1TB NAS drive.
The command line in the Post commands secton is "DateRename.vbs"
The working folder line is "C:\Program Files\Acronis\Scripts"
The parameter line is "/file:T:\TrueImage\C610\Files\dailyfiles.tib" where "T" is the network drive and "/file:" is the required format for the parameter switch.
When the task is run either in scheduled batch or online mode, the VBScript is called and executed, but the parameter line is not passed to it, so the script does not know which file to rename. The same is true when running the test facility if I edit the TI backup task.
However, the script works perfectly if I run it in command line mode with the command:
"cscript.exe daterename.vbs /file:T:\TrueImage\C610\Files\dailyfiles.tib".
Incidentally, I tested this on a WIN7 machine and it ran correctly in all modes.
Would be grateful for any enlightenment,