This indicates that Fiddler attempted to allocate memory at a time when it was already using 14.1 gigabytes, and that allocation failed. Generally, that means that your system has a Paging (Swap) file of a limited size and your physical RAM + limited Paging file simply didn't have enough room to handle the memory needs of all of your applications.
Because Fiddler buffers all traffic in memory for inspection, it can use a large amount of memory if you download a lot (or huge files) and do not periodically clear the Web Sessions list.
- You can use the Keep: dropdown on Fiddler's toolbar to limit how many Web Sessions Fiddler will keep in the session list.
- Click Tools > Fiddler Options > Performance to set a lower "Stream and Forget" threshold (useful if you download large files you don't care to inspect in Fiddler).