Usage monitor gone mad

[#1]

Something very odd is going on with the usage monitor - My usage has jumped from 4-5GB a month to 24GB last month yet appart from a couple of films my usage has not changed. Take this week for example.
Sun  1.57GB
Mon  2.08GB
Tue  58.65Mb
Wed  58.81Mb
Thur  2,9GB
My usage each day has been the same, if fact yesterday appart from a couple of hours browsing in the morning I hardly used anything yet it is showing 2.9GB. Same thing applies to Sunday and Monday. In all the years I've had BB my usage has hardly ever gone above 4,5GB a Month noe it has shot up doing what I've always done.

[#2]

A few things too look aout for
Is you wifi network secure, if not other people can access it and start downloading using your router
if you leave a llist of website you frequent i can point out which ones are bandwidth high

[#3]

Assuming you've considered PiLoT's advice, performing some packet capture using for example something like wireshark could help give us a clearer idea of what is taking up so much bandwidth.
Let me know if you need some advice if you decide to give that a try.

[#4]

Problem is I don't know the bandwidth has been used until I check. I change the PW on my wirless router on a regular basis and use WPA2 encoding so I very much doubt it's getting pinched.

[#5]

In that case giving this a try might be a good idea:
http://www.wireshark.org/
You'd need to send the capture files to us once done but this would help analyse your traffic and identify what's increasing your usage.

[#6]

If you are running PCs a simple watch of the usage might point you in the right direction: http://www.softperfect.com/products/networx/ (even if all it does is eliminate certain PCs as being the problem).