Downgrade links, stupid 1.5.1 Mail by Google doesn't work for me either; if you don't see your device listed, follow the pattern and take a guess on the URL.
GMail v1.1.0
http://mail.google.com/app/v1.1.0/L1/gm-BlackBerry-8100_v4_0.jad
http://mail.google.com/app/v1.1.0/L1/gm-BlackBerry-8300_v4_0.jad
http://mail.google.com/app/v1.1.0/L1/gm-BlackBerry-8310_v4_0.jad
http://mail.google.com/app/v1.1.0/L1/gm-BlackBerry-8320_v4_0.jad
http://mail.google.com/app/v1.1.0/L1/gm-BlackBerry-8830_v4_0.jad
Mail by Google v1.1.0
http://m.google.com/a/v1.1.0/en/MailByGoogle-BlackBerry-8100_v4_0.jad
http://m.google.com/a/v1.1.0/en/MailByGoogle-BlackBerry-8300_v4_0.jad
http://m.google.com/a/v1.1.0/en/MailByGoogle-BlackBerry-8310_v4_0.jad
http://m.google.com/a/v1.1.0/en/MailByGoogle-BlackBerry-8320_v4_0.jad
http://m.google.com/a/v1.1.0/en/MailByGoogle-BlackBerry-8830_v4_0.jad
I just deleted Mail by Google 1.5.1 and installed 1.1.0 and it's not working either like it was before (can't remember when I last ran it, day or two ago?). Maybe it's T-Mobile having a colossal screwup, it *is* raining again.