Data problems, related to jailbreak?

I"m having a bit of data speed issues recently with my jailbroken iPhone 4.

I live in Chicago and have great AT&T service everywhere I go (home, walk to work, in the office). I'm on wifi at home and at the office, so the only time I really use my 3G data is when I'm outside of those 2 locations.

Since I jailbroke my phone a few weeks ago, I've had very poor/slow data speeds. I have full bars showing, but data download speeds around .06-.5 Mbps.

A quick turn on/turn off of airplane mode seems to fix the issue, and I resume getting my normal 1.5-3.5 Mbps speeds in Chicago.

I notice the issue happens when I leave a wifi zone and then move into 3G usage, ie walking to work or taking the dog for a walk. I'll get almost no data download at all until I turn off/on Airplane mode.

Does anyone know what might be causing this? Is it a jailbreak issue? I've been jailbroken before on other iPhones and other iOS versions, but have never had this issue.

Just for reference, I'm on iPhone 4 iOS 5.0 with untethered jailbreak, with the following packages:
Activator
SBSettings
BiteSMS
Browser Changer
CallBar
FakeClockUp
Five Icon Dock
NCQuickDismiss
Sirious
StayOpened
WeeFlashlight

Anyone know what I should do? I already tried to reset network settings, and that didn't seem to work.

Thank you for your help!

 

I used RedSn0w to jailbreak. It's not untethered.

I doubt the data speed issues are related to Sirious. I was having this issue before I installed it.