Hi Gairik;
Please check the browser console for any errors.
We are on sp6 version and it is working fine for us.
Please check whether the url contains the workitem id when you navigate between the items.
Please check this note also for UI correction of sp7
2193142 - W2 /SP08 corrections for the app MM_PO_APV 'Approve Purchase Orders'
Regards,
Sarbjeet Singh