There really isn't much to work with.
First a screenshot of the "constant pop-ups about viruses" might help.
Have you any browser extensions, security add-ons that might be responsible ?
Attaching Images to your post - When you Click the Reply button it opens a text window for you to post your comment (reply or post).
Click the Preview button, that shows what you have input and expands it to include 'Attachments and other options'. Click that it further expands, here you can attach images, etc. at the bottom of your post.
See my attached image, click to expand.
