It's very unlikely that the XMRV virus alone could be involved in your vomiting. Although the research on XMRV is quite new and what is known about its ability to directly cause symptoms is unproven, like HIV this retrovirus apparently has the potential to cause immune dysfunction. The immune dysfunction could be involved in your problem, or it could allow co-infections that are know to actually cause symptoms to become entrenched in your body.
Some experts think that the XRMV (like other retroviruses) is insufficient by itself to cause morbidity, thus it may or may not be necessary, but it appears not to be sufficient by itself to cause disease.
I am XMRV positive (was in the WIP study) but my docs here and at Mayo were scanning and biopsy-ing and blood and urine testing me like crazy for two years, sure that I had a malignant pheochromocytoma -- I have tumors in the liver and spleen that looked metastatic, sky-high catecholamine levels, heat intolerance, vomiting, sweating. Absolutely you can vomit with XMRV.