Hi all

Many thanks for the pointers and tips.

My lateness in replying was down to the multitude of work as per the usual last minute why have you stopped working moment! 

The issue lay with quicktime in the end. DusX's suggestion made me actually think about the problem as opposed to just restarting and hoping for the best.

 I went into the activity monitor and discovered that quicktime was frozen and taking up no RAM space etc. I quit the process and restarted. All worked fine and has done since.

I had never seen that type of issue before. I realised I had tried VLC but not actually Quicktime. It seems that the quicktime engine had a mild stroke etc. The computer in question is doing a lot of other jobs in terms of gallery control and I do not really have another spare unit like it. I have spares but would require a bit of work to reset this system even with file back ups.

Problem cured and all resolved.

Many thanks again

eamon