I have Cox HSI in the Phoenix, Arizona area, with the 4000/512 package.
I have been getting exactly that until recently, my download speed has been dropping. Ive tried everything I cant figure out what the problem is. I've started to get many connection problems while playing BattleField 2 demo. My upload speed seems good, around the 500 range. Download speed was dipping between 4000 and 1000 yesterday. Today im getting between 1000 to 500... very bad.

My cable modem signal is as follows: (Surfboard SB 4100 Cable Modem)

Downstream  Value
Frequency 579000000 Hz Locked
Signal to Noise Ratio 34 to 35 dB
Power Level -1 dBmV
 
Upstream  Value
Channel ID 3
Frequency 19600000 Hz Ranged
Power Level 44 dBmV 

when I took off the splitter the power level increased from -1 to +2 db, but this didnt help.
Please someone help I dont know what the problem is.

Also I have a Dlink DI-604 Router but I dont think this would be causing the problem.
I read that recently they upgraded the premium service (wich I dont have) to 9Mbps wich is a huge increase, could it be that the line has become overloaded due to this? I would I hope that cant happen but I really dont know what to say.
Shed some light on me if ya can 

Ok now at 12 midnight here is my results:
::::::::::.. Download Stats ..::::::::::
Connection is:: 4062 Kbps about 4.1 Mbps (tested with 5983 kB)
Download Speed is:: 496 kB/s
Tested From:: http://testmy.net/ (server2)
Test Time:: Tue Jun 21 00:25:16 MST 2005
Bottom Line:: 73X faster than 56K 1MB download in 2.06 sec
Diagnosis: Awesome! 20% + : 27.98 % faster than the average for host (Cox.net)
Validation Link:: http://testmy.net/stats/id-T4PFKAH3W

This is seeming more and more like their line cant handle the new 9Mbps load durring peek hours.. either that or they just happened to fix whatever the problem was. Owell I will update tomorrow.