Rebooting the system restored the proper speed, so it was clear the suspend has something to do with it.
The solution that worked for me: I've put in /etc/pm/config.d/config this line:
SUSPEND_MODULES="ath9k"Where ath9k is my wireless driver.
If /etc/pm/config.d/config doesn't exist, just create it and add that line (changing ath9k with whatever driver is bothering you while suspending)