To address this 'problem' you should use some intermediate signals (unique for each process) and then combine them.
Example: two processes driving the same signal:
Code:
process(...)
begin
..
signalout <= ...
end process
process(...)
begin
..
signalout <= ...
end process
gives you this error.
Use the following instead:
Code:
signal signalout1: ..
signal signalout2: ..
process(...)
begin
..
signalout1 <= ...
end process
process(...)
begin
..
signalout2 <= ...
end process
signalout <= signalout1 or signalout2; -- Use some selection (like 'or' 'and' 'select' 'if') to combine the individual process signals
For processes you could also combine the two processes into a single process, but this is not advised.