No category selected error when submitting

[gragland]

I don't want categories for my site, so I have the category select box hidden on the submit page and it's checked by default so that you don't receive a "no category is selected" error when submitting. But some users report getting this error and are unable to submit.

<li style="display: none;"><input name="category" type="radio" id="select-i" value="1" Checked/>pligg</li>

Is there something wrong with this code I use to hide it and have it checked by default? I haven't been able to reproduce this error, but a lot of users are having this problem.