I have 32-bit Vista with IE7 (7.0.6002.18005) and it works fine
with remembering the login for MyNissanLeaf.
So, it is likely some other program that interferes with IE7 or
some cookie (setting or reading) or security-related (like firewall)
seting. I use the standard Vista firewall, with no unusual setings,
and AVAST for anut-virus.
Under Tools, internat Options, Security, I have selected "Medium".
What do you have running, or what settings, are different?
See SOC/GID-Meter and CAN-Do Info
2011 LEAF, sold in 2015
2010 Prius, 2014 silver Tesla S
Nissan EVSE, mod to 240/120v 16A
Solar PV: 33 x 225W -> 7 kW max AC
To Sell: X-treme 5000Li EV motorcycle