Youtube Uploading Problems

[Lov3shy]

Heya

As an avid user of YouTube, I love to look through videos as well as create my own. I love being able to have that freedom of uploading videos, but unfortunately I can no longer do so anymore!
I go to the upload button and go to 'Upload Video File'; instead of a bar with browse next to it, it just has a box that says Upload Video'. With both it would ask me to locate the file to upload (which is good).

However, with the one that doesn't have a search bar to upload, it says it's uploading the video but then stops saying this - "Upload Failed: An unknown error occurred."
Previously I was able to upload videos and the search bar way came up to which allowed me to upload properly without a failure. But I don't know why I'm unable to upload.

Now I'd rather not download any software to aid in this (more notably the YouTube uploader) because I'd prefer to upload my videos using the allocated file upload on the YouTube site itself, but I don't know why it's not allowing me to upload. This is with all files and changing the file to an MPEG-4 (most appropriate for YouTube) doesn't solve the problem.

So why is this? And what can be done to resolve it?

Many thanks