[xlguy]

Originally Posted by MarcoH64

Upgrade to 3.5.4
Reset your cookie domain/path to default.
Create a new Style with no Parent set, let your members use this new style, and see if they still have problems.
Try disabling the Page compressor hack.
Turn off GZip-compression in your vBulletin Options.
If still problems, disable all hacks.
Make sure your members who are reporting this are checking Remember Me box when logging in.
What is the setting for you Cookie timeout?

Thanks for this Marco, I have already tried resetting the cookie path. The timeout is the default (900 I think?). At the moment users are indeed using a child style, so I will give your suggestion a go. As for "Remember Me" I have that set to checked automatically. The problem was happening before Page compressor so I'm confident it's not that. Cheers.