Adobe Illustrator File Not Opening Without Full File Name (.ai)

So this issue has just started not to long ago where I would be opening up a file that is already saved so I can edit it, but when the file name appears in the suggestion box below I would hit enter. But when selecting the suggested file with the enter button an error code will appear "File not found. Check the file name and try again" on a file that I know I have and can open if I were to enter the file name again and then tack on .ai at the end or by selecting the suggested file with my mouse. Only then will the files open normally. Can anyone inform me what is going on with this? I am currently on CS5.