Thanks guys,
I did that and now it re-downloading all the blocks. Any idea what caused this issue?
I don't want it to happen again.

I purchased bitcoins today and when I got home bitcoin said something about an update needed or nodes needing upgrading or something.

I closed bitcoin and now when I try to open it I get a runaway exception

EXCEPTION: NSt8ios_base7failurE
ReadCompactSize():Size too large
"my c drive address"\bitcoin\bitcoin-qt.exe in Runaway exception


I haven't tried anything because I'm new to this and don't want to jeopardise my bitcoins.

Any help would be greatly appreciated.

Thanks guys

B

PS I am running Windows 7 if it is relevent