My b2evolution Version: 1.8.x

Hi.
I'm having this weird error when I try to upload an image, for instance:

Firefox: in the pop-up window, it says:
<!-- if( opener && opener.document.FilesForm && typeof(opener.document.FilesForm.md5_filelist.value) != 'undefined' && typeof(opener.document.FilesForm.md5_cwd.value) != 'undefined' && opener.document.FilesForm.md5_cwd.value == '70b4a42b88286ab5bf1331f1c6b93e44' ) { opener.document.getElementById( 'fm_reloadhint' ).style.display = opener.document.FilesForm.md5_filelist.value == '

Internet Explorer: in the pop-up window, it says:
Error in the page.
Line: 252
Character: 3
Error: first_form is null or not an object
Code: 0
URL: http://blog.oleschmitt.com.br/admin.php?ctrl=files&mode=upload&fm_mode=file_upload
And just the title "File Management" appears.

This "first_form" was found inside "/rsc/js/form_extensions.js"

I've replaced this file with an original one, but the same error is still occouring.

I've made a lot of research here in Forums before asking for help. And yep, I still have the 1.8.x version and I'll upgrade soon, but I'd like to be able to upload images while this doesn't happens.

I've changed my hosting, but I was able to upload only 1 (one) image. When I tryed the second time, this happened.

All file and directory permissions checked and rechecked. User permissions (under b2evolution engine) also.

There was a girl here in the forums with a similar error, but I wasn't able to understand what she did to solve that.

Thanks a lot.