"Copying messages to saved folder" 

Hi, I have been running Mozilla Thunderbird since the beginning of the year. I have always had problems, but it seems to be getting worse. It won't download messages, it won't save messages at the time you send them, instead a window runs for ages saying: "Copying messages to saved folder" Then it says "There was an error saving the message to sent, retry?" You hit cancel and then it comes up with: "The message was sent successfully, but could not be copied to your Sent folder. Would you like to return to the compose window?" Then there is the problem of downloading messages, basically it doesn't all the time, it hangs and I have to either restart the computer or download them on my iphone. It can take upwards of 20 minutes to download a single message. I had a look at the "Activity Manager" and it seems frozen as well. It also sends up the messages that the server has been disconnected or timed out. I've had a look through the trouble shooting guide but can't seem to progress this. Any suggestions will be greatly appreciated! I am running the latest version, and have Windows 7, 64 bit. I am fast of the opinion I'd better shell out some cash and get Windows Outlook as Thunderfox is a nightmare. Many thanks, Adrian