I wonder if your machine overheated when running iPlayer, and the resulting crash corrupted something.
I build my own PCs, and as part of that process I need to ensure that the cooling of all the components is adequate, and I research the operating temperature range of things like the CPU, graphics card, memory, hard drives, etc.
Fortunately Ubuntu (before version 11.04) allows you to add temperature monitor applets on the notification bar, so you can get a coloured thermometer style display of the various components temperature on your desktop making visual monitoring very easy
I'm telling you all this because from experience my machines normally run perfectly happily and run cool 24/7, HOWEVER when running iPlayer for more than say two hours, so much CPU and GPU resources are used that the machines often heat up to towards the upper limits of their designed temperature range. I could easily imagine that if your PC's heatsinks and fans were a bit dusty, or the PC was located in a position that restricted airflow, that long iPlayer usage could induce overheating.
It is not only the CPU and GPU that are affected by temperature, on 'budget' mass market built PCs, the manufacturers often fit the lowest spec memory cards that they can get away with. Unfortunately if you raise the ambient temperature of the case too high, then memory timing characteristics change, causing corruption of the data, and consequently to possibility of corrupting the files subsequently saved to the hard drives.
This is one of the reasons that when you fit new memory to a PC, you should ALWAYS run a memory diagnostic program such as
MemTest86 for 24 hours with the PC case CLOSED. I now fit memory that is at least on grade faster than the motherboards maximum, as I have found that eliminates temperature related timing problems - especially if you go in for some mild overclocking !
Some better motherboard BIOSes have a feature for setting an audible over temperature alarm, where you can specify at what temperature the motherboard starts screaming at you that it's too hot (usually with a fire engine siren type noise !). For Windows PCs, on the manufacturers 'drivers' disk that come with the PC, there is often a system monitoring program that you can install, that sits in the background that will warn you if anything needs attention. Most people never even bother to look at those driver disks, so are unaware of those useful little utilities.
So keep an eye on temperatures, and if it starts getting too warm, consider first cleaning out the dust, and then fitting more or bigger fans.
