Daisy, Yesterday (and for a while the night before) the forum website was out of action for quite a long time (sorry about that - malicious internet activity affecting many forums, which we hope has now been dealt with). That would have foiled your attempts to post completely, but I don't think you would even have succeeded in calling up the forum in the first place.
So perhaps the trouble is that your session length setting has somehow been altered. Try this:
In the line of blue tags towards the upper left corner, click on the LOGOUT tab
Then when you get the Welcome Guest scree, put in your usual user name and password, and make sure that the login session time is set to Forever.
Hope that fixes it; if it doesn't the fault may possibly be with your own internet connection dropping out temporarily.