Problems with logins on websites

[#1]

Hello. I'm new to PlusNet  broadband
At the moment my internet access in general seems to be doing OK, and I can get to most of the websites which I use regularly, BUT......I seem to have problems whenever I try to login to a website somewhere, especially online banking sites or similar
The main website pages will load OK, but as soon as I click on the 'login' link I get the 'connecting' message and then everything just seems to go to sleep for a-g-e-s. This even happens on parts on PlusNet !!
Might this just be a temporary glitch of some sort, or is it a feature of a known problem please? I recall something similar years ago now to do with MTU or MRU settings.

[#2]

Hmmm, some more information please.
Have you connected via a different ISP in the past at this location?  If so, was that OK?
Are your using wireless or wired?  Can you switch?  Does it make a difference?
Have you tried a different computer at the same location?  Did it have the exact same problem?
Jason

[#3]

Could be a problem with how your browser deal with secure web sites, https .  Have you tried an alternative web browser?

[#4]

To answer the various questions:-
1. I never had this problem with my previous ISP on the same phone line
2. The problem occurred on two separate PCs on my LAN, one wired and one wireless.
3. Switching the wireless PC to wired made no difference.
4. Browser is IE8. No obvious problem with https sites before (see answer 1 above).
Today - fortunately - the problem does not seem to exist one ither PC, so maybe it was just a temporary glitch after all ????

[#5]

The only thing I can think of is run an up to date virus check on your PC's.