Replaced w/ what card? Be specific. Brand, model, specs, etc.
As previously suggested, you need to revert to a version of Mac OS supported by your 2009 iMac (w/out OCLP involved). Eliminate all those 'upgrade' variables. If the installed WiFi card doesn't work on a supported version of Mac OS then it's either the card or an issue w/ the logic board.
Have you tried resetting PRAM or SMC on boot?
If you're experiencing weird glitches with your Mac, doing a reset of your MacBook or desktop Mac could help. Here's how to reset the NVRAM, PRAM, and SMC on either an Intel or M-Series Mac.
www.macworld.com