A couple of things...
The break-up of Martina's partnership with Arantxa and Natasha were mutual decisions. In so many ways, you can say Arantxa and Natasha have done "MUCH" better since the breakup - Arantxa with Hantuchova, Zvereva with Rubin.
Secondly, Martina playing with different partners over the summer was simply to play with different partners. She could not find a regular partner as everyone has more-or-less committed to someone or the other and it was the middle of the year. This partnership with Serena is a one-off for the most part. I really do not see Serena playing with Martina at the Slam events. And Martina approached Serena with the idea at Wimbledon this year. This hasn't been some recent brainwave.
Martina would much rather have a regular partner - she played the entire 2001 with Arantxa - but she has had few choices this year.
P.S. and for the record, Martina has never played with Panova.