My ThinkPad T43 had a number of flaky and oddly inexplicable issues with bluetooth, using the MS supplied drivers
. It now behaves much better after installing this Broadcomm WIDCOMM Bluetooth Software
for windows package.
Mine is a 32 bit system. It is also a significant revision older than your T61, however I'm betting your BT module is also a Broadcomm (windows refers to mine as an IBM Bluetooth Module in a couple of places, but it's a Broadcomm. The Broadcomm page doesn't say anything about being for 32 or 64 bit only, and only offers one download (which is an installer that looks at your system then fetches the actual drivers) so it's probably a combined package for 32/64. Made everything better for me, YMMV.
Hope this helps.