Steve, it's not uncommon for a BCD to fill with water during normal use - some more so than others, and it depends on how you vent the air on descent.
For example, my old Scubapro BCD would take on gallons of water if I used the pull dump to deflate, and much less if I used the LPI deflate.
Your best bet is to empty the BCD of the salt water and give it a good rinse inside. It's when the salt water dries and leaves crystals that you'll get a problem. I'd then inflate the BCD so it's full (bulging!) and leave it over night. If it's still full the next morning, then I don't think that you have a problem.
If it's even just slightly deflated, then you may have a leak. First of all, check that all the connections are tight - particularly where the LPI hose screws onto the BCD - I had a new wing recently that came which leaked because this wasn't screwed up tight. Then inflate the BCD fully and sponge soapy water over the surface. A leak should be fairly obvious as the soapy water will bubble somewhat even with the smallest of leaks.
I guess if it leaks, you've got several options - take it back to the guy you bought it from, or try and get it fixed. Depending on the make and style of the BCD, and where it is leaking, determines how easy it will be to fix. The worst case scenario is a leak on the seams - not uncommon with kit owned by relatively new divers, who put on way to much weight and then do giant stride entries with the BCD fully inflated.... this puts a lot of stress on the seams, often causing them to tear slightly even with new kit.
Hope this helps.