Is it the same number every time?

try deleting hostlist.txt first, as that's the easiest and least impacting of any possible fixes (if it happens to be a corrupt resumeinfo.txt file.

Try looking for the number as a value in HKEY_CURRENT_USER/SOFTWARE/XOLOX (use regedit, or regedit32 if you have XP (or NT?))

If it's there, try setting the key to something that's allowed. For a list of registry items XoloX uses and values that can be put in them (that I knew of), go <<here>>

Or you could just delete the whole XoloX key alltogether, XoloX will create it again at launch. You will have to go and change back al your settings though.

If you find nothing wrong with your registry keys(or you just deleted your HKCU/Software/XoloX key) and still have the prolem, my bet is a corrupt resumeinfo.txt file. If you have no important downloads going, just delete this file alltogether and see if that helps. If you do have important downloads going, you may be able to salvage a few by:

1) Open resumeinfo.txt in notepad.
2) Scroll down to the very bottom. (Ctrl+End)
3) Highlight up-to, and including, the first JOB-# line you come to.
4) Deleting the selected text.

If you still have the problem... I dunno, try unindtalling, deleting the registy key HKCU/Software/XoloX and re-installing (if desired)