I have this problem with Ubuntu 0.4.9 version too. Nothing seems to work to fix it. I will wait for the next wallet version...
If it helps, in my case I had crashes almost every time some of my orders where filed in the market(EDIT: while I was using the 0.4.8 version), it appeared that the crashes were random but every time I instantly restarted my wallet I saw incoming transactions from market. Last think I remember is trying to cancel the two market orders I had in market, the client crashed a few seconds after I clicked "cancel", then I upgraded to 0.4.9 and I'm having these issues...