Tricky one that. There are lots of potential causes and a fair few possible solutions too mate. Have a read of what I can think of:
Firstly, what type of laptop do you have (Make/Model)?
If you try whats below and it doesnt work, this would be useful to know.
Do you know who makes the Wireless Card (look in Device Manager under Network Adapters)?
If you access the properties of the Wireless Card (through Device Manager), look at the Advanced tab if available and have a look for a setting called Roaming Aggressiveness This setting dictates how often the Wireless Card will try to search for another Access Point with a potentially better signal, but as you only have the one, you could probably get away with setting that to the lowest value.
You can also have a look for Transmit and/or Receive Power settings, they can be set to the maximum level and also have a look for Power Management Your laptop might be configured to save power by disabling the Wireless card when not in use, so set it to Always on or Constantly Awake if you can.
Does Windows control the wireless settings or is it another 3rd party application from the makers of the Wireless Card? Some examples:
Belkin
Intel
Atheros
Cisco
Buffalo
Broadcom
Netgear
Linksys
If its not Windows thats controlling it, your problem could be that the Windows Wireless service (Wireless Zero Config Service) is interfering with it. It can be disabled, (Start Run Services.msc Double-click Wireless Zero Config Service click Stop and Apply then set the Startup Type to Disabled) If it is controlled by Windows, doing that will stop it working altogether but its easy enough to set it back again to Automatic.
When its connected, what kind of signal strength are you getting?
Do you notice anything happening just before the Wireless drops off?
Anything electrical near/between the laptop/Homehub that could be interfering?
Anything in the event log to suggest there might be a problem with something?
Does it re-establish the connection of its own accord or do you have to manually re-connect it again each time?
Are there any other machines connected wirelessly to the same Homehub? Do they suffer from the same problem?
Have you tried updating the Wireless Card driver or Wireless Utility (if its a 3rd party application)? They can usually be obtained from the manufacturers (either that of the laptop of wireless card) website
Have you got any Anti-Virus/Firewall/Anti-Spyware software? Are they up-to-date? Is your machine squeaky clean?
Good luck,