Iphone 3G not charging

[thawk21]

I went to bed last night and my phone was pretty much fully charged. I woke up and it was at less than 20%. I thought it was odd but I started to charge it through my computer. After about an hour I checked it and I still get the 20% battery warning. When I plug it into my computer it goes through the sync as normal and the phone has the icon like it is charging but it just won't charge. I have tried a full reboot a couple times but still not working. Any ideas on what is wrong and what I can do? Thanks

 

[raison]

Try to let the battery drain all way and try to charge it. If it
works, repeat the same process. P