crm 2011 all form javascript causes an error

Hi All

I hoping someone can help with this . I have issues with some javascript errors which are thrown when ever I attempt to add javascript to new entity form.

I've had some code there previously and it worked fine and then for no apparent reason started throw errors. I got to the point I removed the code completely and the problem went away as expected. So I then attached a new script containing single function with an alert just to test as I could not find a valid reason why orginal code failed.

sample code fired by the onload event

function test()
{
  alert('ok');
}

This also producted the same error

FormScript.js.aspx?formid=4392d8fc-2ab3-46b1-8c65-0e6bb8df4f44&FormName=crmForm&fver=-1277710970&isbulkedit=false&ver=-111192425, line 1 character 1

main.aspx?etc=10008&extraqs=%3fetc%3d10008%26pagemode%3diframe%26preloadcache%3d1375661742664&pagetype=entityrecord, line 1 character 14825

Does this make sense to anyone and how I might get passed it.

Thanks in Advance