This page may be some help to you if any of the following things start happening on your BBC with no apparent explanation:
1. When I type statements in BASIC I get "Mistake" or "Syntax error" even though what I have typed is correct.
2. When I get an error from an Econet command, the error message is all in lower case letters.
3. When I press BREAK or switch on, all I get is a * prompt without the usual message and sometimes a few lines of random characters.
4. When I catalogue a directory or list a programme, the output suddenly shifts half-way across the screen part way through.
These errors can be quite worrying, making you think that your Beeb is on its last legs. Do not despair - I have discovered that one simple thing causes them all - bad contacts on ROMs.
Somewhere, there is a bad contact on a ROM which is playing havoc with your BBC micro. In the first instance, switch off and check all your ROMs. Make sure they are pressed firm in the sockets and there is no dirt or dust preventing a good contact being made.
Pay particular attention to anything involving ribbon cables like a ROM Box or the BBC micro Viglen Cartridge System, which seems to be particularly troublesome in some cases.
On the Master, check that good contacts are being made on the cartridge slots. The contacts on ROM cartridges tend to get dirty or wear away over time so check these. Also make sure that no dirt or rubbish has fallen into the cartridge socket on the Master. This happens quite often when the surface of a ROM rubs against the Master casing as you are inserting a cartridge, rubbing off the ROM label which eventually finds its way into the socket.
In most cases, a good spring clean around all your ROMs will restore your computer to new. If the problem persists with a particular ROM cartridge then I would recommend replacing it as they do appear to develop faults over time.