So, unless you are really cheap and want to "fix" it yourself by puncturing the battery cases to release the gases (not something I would do but others have successfully), then get a new battery. BTW, running it all the time on AC is not recommended. I think my problem was exacerbated by doing that myself initially.
Manufacturers of Li-ion batteries refrain from mentioning explosion. ‘Venting with flame’ is the accepted terminology. Although slower in reaction than an explosion, venting with flame can be very violent and inflicts injury to those in close proximity. It can also damage the equipment to which the battery is connected.
http://www.buchmann.ca/chap3-page6.asp