There could be several reasons, starting with corrupted data, overloaded io system so the read/write timed out, etc.
I favor a timeout, depending on number of users, number of dbwr's, whether async i/o is allowed, and some other factors.
Basically, due to stress.
But this is guessed in ignorance of your platform, system and database configuration.
More information is needed. Sometimes this error is an annoyance (if a read only cd based tablespace is not in the drive), sometimes a symptom of a system problem (drive going bad). Were there any other messages association with the one you cited.
Joseph R.P. Maloney, CSP,CDP,CCP
'The answer is 42'