Hi,
Certainly you have exceeded the snapshot limit.
- The maximum supported amount in a chain is 32. However, VMware recommends that you use only 2-3 snapshots in a chain.
- Use no single snapshot for more than 24-72 hours.
Since you have 250+ in the chain,the best way to get the data is clone the disk via cmd line>http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1028042.You can go ahead and select the right datastore(destination)which has enough space.Also do check the largest snapshot in the chain and do start with the same,if you are fine to skip few others.
Moving forward to ensure we are not going to end up with same scenario,i would suggest you to go ahead configure alarms which will trigger whenever a VM is running on a snapshot>http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1018029