Almost all internet connections, whether dial-up or broadband, will start at very high transfer speeds and then settle down to what your limit is. You say you have a 512 connection. This means your download speed is 512 kilobits/second....not 512 kilobytes/second. 512 kilobits/second = 64 kilobytes/second. You're getting a rate of 30 kilobytes /second. While that's slower than what your connection is rated, there is rarely a time when a connection transfers at its max. I hope all of that made sense!!!
Edit: however, if your rated speed is 512 kilobytes/second, then it could be several things. I would try a new telephone line or cable cord(depending what type of broadband you have). If that doesn't work, try another ethernet cable. If that doesn't work, you could have a problem with your broadband modem.