Hi Ashley Brown,
This does sound odd, especially if your phone is picking up 3G+ HSDPA without issue
Can I suggest trying to swap SIMs between your Jet and Modem? Does this result in any difference?
Also, can you try a short USB extension cable between the Modem and your Mac? This may reduce any interference issues that may be plagueing your connection - it's rare but can sometimes happen.
Also, how's your connection speed outside of your home/building? It might be worth noting if different rooms affect your connection.
The reason why it bumps up or down to a different connection bandwidth is because the modem detects stronger connection signal with the band and transfers to it - this will result in a short pause whilst the modem adjusts.
I've checked your area and it appears that you're next to a 3G site - have you noticed if specific times of day are affected in particular? It may be the cell, and with some furth info we'll be able to hone in on the specifics of the problem!
Hope to hear back from you soon,
Daz
eForum Team