Not working

[Cassandra]

At about 11.30 4.2.4 I logged on and I could access my user cp but could not post replies or use the PM system. Then it started working again. Why did it do this and how can I fix it if it happens again?

[Admin]

That shouldn't have happened. Perhaps your session simply expired.

[Cassandra]

I hadn't been on very long if at all. I often seem to have trouble getting on.

[Admin]

What browser do you use?