Bad Earth??

[x DTR x]

Hi all
After owning my 99 Gdi for just over 3 years now she has never failed to start, but after already driving it 15 miles this morning i stopped to get some fags and it was turning over like the battery was about dead and wouldnt fire up? As i was only round the corner from work, one of the lads came round to give her a jump but this had no effect and just smelled like the jump leads were melting (yes they were on right way round)! We came back about 20mins later with a transit and some heavier duty leads and she fired up straight away and when i left work this evening she started no problem but was asking for the radio code which i thought odd too? This has happened a few times now after driving about the same distance but has always just about fired up. I am charging battery at moment but not showing that it is flat and was wondering if i had a dodgy earth somewhere hence the smoldering leads which i know/were perfectly ok?

Many thanks for any advice