What does this mean. ( out of memory after server mov)

[davio33]

I moved from a shared host to a vps

It has been a nightmare. Now on the vps ...Site crashing, swap and memory now being used up.

Host recomended a more expensive hosting package.

But today i looked at my error logs. The fatal error "out of memory" message never showed up until i was on the new vps, the date of the move corilates exaclty with the out of memory error message.

So my question is. If i wasnt getting this on the old account, but get it on the new, what would this tell me?

Thanks