The speedhack detected system you are running into is a sever side setting (which can be turned on/off and configured by server admins). It is looking for clients running out of sync with the server (the most common say to speed hack). However false positives can occur when a client is having network issues and not syncing up with the server as fast it should (most often caused by dropped packets/packet loss). The most common cause of this is a wireless connection or an ISP throttling the games traffic.
If you are running a wireless network and cannot switch to a wired one, we recommend trying this tool to address packetloss over your network: http://www.martin-majowski.de/wlanoptimizer/