That sounds mighty like McAfee anti virus. What are you using?

Alforster said

It does not matter whether you use the attach command from the tool bar or wait for Thunderbird to pick up the word attached from your text and then attempt to attach a document. As soon as you attempt to attach the item the program freezes and you are asked whether you would like to close the program or wait for Thunderbird to respond. Last choice Not recommended by the way.

Hi Matt I am using Avira Anti virus

With that clue re anti virus possibly being the problem I turned off outgoing mail scanning in Avira and proceeded to send a test email with attachments. I was able to attach documents and pictures without issue. I guess turning it back on and performing the test again will confirm the problem lies with Avira. Thanks Matt

Further testing is even more perplexing. It has nothing to do with the anti virus mail checking being on or off. You are able to attach a document so long as you do not attempt to use the slider function to search down say for example the document folder. If you do it freezes and the attach function is unresponsive. If you select attach and then pick a document that is visible when the attach screen opens and do not attempt to look by using the slide function all is well.

bizarre suggestion for a bizarre problem

try the fix here https://support.mozilla.org/en-US/questions/1012145

I really am grasping, but it has been responsible for some truly weird graphics issues.