You are using Forms 9i with JInit on a windows 7 and IE8, probably with the hack to replace the jvm.dll. Letting aside that this combo was never tested against each other (at least not forms 9i with IE8, I omit JInit) that's why you shouldn't use that stupid hack. It is most certainly caused by this hack. So go ahead and use the JPI instead JInit and while you are at it you might even want to upgrade to a more recent version of forms.
Besides that the Forms version you are using has long been desupported and the configuration on which you are using it was also never supported, there are likely several reasons why you are having problems. However, depending on exactly how you are using WEB.SHOW_DOCUMENT may be part of your problem. If you find that JRE versions older than 1.6.0_24 work correctly, but newer ones do not, this is likely caused by a known issue which was corrected in newer Forms versions. Details can be found in Oracle Bug 11879934. Because you are using such an old Forms version, no patch is available for that issue in that version.