Everytime I try to upload, I fill out the lyrics and title and then I upload the file. When I click upload, my computer thinks for a while, then the fields wipe clean and everything goes away. This has happened at least five times, and I just can't get it to work. 
My song is a .aif file, and I don't know of any other potential problems. Can someone help me?

An .aif wont get uploaded, you'll have to convert it to an MP3.
The site has had problems with MP3s too, and the best solution was to convert in iTunes and not have any strange characters in the title name.
If you fill in the Genre tag field when your converting it should be picked up by the sites code.
Does this help?
And welcome to the Amp      

How are you uploading the Lyrics? It sounds like you are trying to upload them at the same time?

WELCOME!!

'audio/mpg',
'audio/mpeg',
'audio/mp3',
'audio/x-mp3',
'audio/x-mpeg',
'audio/x-mpg'

any other file types than listed will fail upload
do not use hyphens in the title

in addition to what was said, try to read the FAQs or use the following link

http://about.bandamp.com/faqs.html#VXBsbFkIGVycmycw

thanks. Now I just need to figure out how to convert my .aif....

download iTunes and use it just to convert.   
So what kind of music do you make?

iTunes is a really good tool (even ripping)

Just checked another freeware Switch Audio Converter Software by NCH Software

converted a 15mb aif to mp3 (256k)... sounds good, no problems

Another free sound editor that will accept .aif files is Audacity http://audacity.sourceforge.net/. Just load the file into Audacity and choose "Export as MP3" and that should do it....

I mention iTunes specifically above, it was a PX tip a long time ago, I was converting with all kinds of programs but it was the iTunes 'conversion' that finally uploaded. It could have been a cookie thing at the time because all kinds of mp3s are uploaded, I just like to mention iTunes in times of need...I personally hate it !  

Yeah I use audacity and it works fantastic