Wubi freezes, won't let me get into Ubuntu

I recently installed Ubuntu 11.10 using Wubi dual boot for my laptop (Dell Inspiron N5040, running originally Windows 7 Home Premium, Service Pack 1). The first time it went well..but after running the required updates and adding some programs and apps, now whenever I attempt to reboot up, the screen freezes to a purple blank and the boot just freezes. Would it be possible to create a start-up boot disk to get into Ubuntu so that I can troubleshoot the problem and resolve it?? Or, would it be better to simply delete Wubi and run Ubuntu from an alternative source? I would still like to keep my Win 7 partition, but I don't want to lose the flexibility of Ubuntu, either. Thanks for your help in advance.