By a keylogger? Maybe, just run your AV and anti malware programs. If they turn up nothing, fire away.
Someone also suggested using the on screen keyboard and clicking the numbers instead of typing them. That way the keys can't be logged, but of course mal ware can take snapshots of the screen.
In summary just make your system is clean, by running your anti-virus and anti-spyware programs and make sure there is a fully fledged firewall like Zone Alarm free edition on board. Windows firewall is useless.