Does it still give the red 'X' with the new battery? If it didn't then, I'd start to suspect the AC adapter.
I have one yoyo adapter which refuses to charge the battery on my Pismos (and I think on my Lombard, though I haven't checked). It powers the 'Book just fine, but won't charge the battery internally (also works fine with VST charger). The version of ASP with Tiger actually has an entry under Power which reads something like "AC Adapter is unable to charge battery: Yes". I suspect that something is amiss in the 1-wire communications between the Pismo and the AC adapter.
If you've got another AC adapter, it's worth a shot to see if that makes a difference.
I have one yoyo adapter which refuses to charge the battery on my Pismos (and I think on my Lombard, though I haven't checked). It powers the 'Book just fine, but won't charge the battery internally (also works fine with VST charger). The version of ASP with Tiger actually has an entry under Power which reads something like "AC Adapter is unable to charge battery: Yes". I suspect that something is amiss in the 1-wire communications between the Pismo and the AC adapter.
If you've got another AC adapter, it's worth a shot to see if that makes a difference.